Foundation for an underwater habitat

Abstract

P087817GB / P190.01 50 Abstract TITLE: Foundation for an underwater habitat The abstract describes a foundation for supporting an underwater habitat on the seafloor. The foundation includes at least one leg configured to engage the seafloor. A foundation 5 connection interface is configured to mate with a habitat connection interface of the underwater habitat to attach the habitat to the foundation. The foundation provides a stable and adjustable support system for underwater habitats, allowing them to be deployed and recovered more easily and efficiently. Fig. 1(a)10

Description

[0001] Foundation for an Underwater Habitat

[0002] Technical Field

[0003] [1] The present disclosure relates to systems and methods for deploying an underwater habitat to the floor of a body of water. Specifically, the disclosure relates to a foundation for supporting an underwater habitat on the floor of a body of water, and methods and systems for facilitating deployment and recovery of the underwater habitat.

[0004] Background

[0005] [2] Various types of underwater habitable vessels are known including submarines, submersibles and underwater habitats. Submarines and submersibles are structures that are both able to propel themselves underwater and enable humans to live below the water’s surface for extended periods of time, for example, several hours, weeks, or even months. Underwater habitats are structures that enable humans to live below the water's surface for extended periods of time, for example, several hours, weeks, or even months. Underwater habitats enable scientific research and underwater exploration to proceed much more efficiently than is possible when diving from the surface since there is no need to decompress between excursions from the habitat. Unlike submarines and submersibles, underwater habitats are not typically able to propel themselves and are instead deployed to a stationary location on the seafloor by a support vessel or shore-based crane. The enclosed interior volume of an underwater habitat supports a breathable atmosphere so that humans can work, rest, eat, and / or sleep in the habitat during the course of a mission. Underwater habitats can be permanently or temporarily deployed to a location, depending on a mission’s requirements. However, there are several challenges associated with deploying, securing, and recovering underwater habitats from the seafloor.

[0006] [3] One of the primary challenges is securely anchoring the underwater habitat to the seafloor. If the habitat is inadequately anchored to the seafloor, forces applied by currents and waves may cause the habitat to move uncontrollably. At best, this might cause discomfort for the inhabitants, affecting their ability to work. At worst, this may cause damage to the hull, allowing ingress of water and putting lives at risk. This challenge has been partly addressed in the past by providing the underwater habitat with integral legs (such as Conshelf II) or by providing a base plate or foundation to which the habitat is attached (such as the Aquarius Reef Base). In the case that a foundation is used, it remains necessary to securely attach the habitat to the foundation.

[0007] [4] Another challenge is securing the underwater habitat in a level orientation, i.e. , such that the decks of the habitat are horizontal (to facilitate living and working in the habitat) and not at an angle. Seafloors which slope and / or have irregular topography created by bumps, rocks, and other irregularities, for example, can prevent the underwater habitat being deployed in a level orientation. Deployment in such locations is either uncomfortable if the habitat is slightly off level, or impossible if the gradient or bumps are sufficiently large as to prevent safe deployment of the habitat at that location in the first place. Moreover, even if the habitat is secured in a level orientation, maintaining that orientation in the event of subsidence or scour of the seafloor beneath the habitat, which may be a particular issue on sandy or muddy locations, may be challenging.

[0008] [5] A further challenge is that it may be desirable to recover the underwater habitat from the seafloor for various reasons, such as repair, maintenance, refitting, or mission completion. Leaving the habitat on the seafloor after mission completion may result in harmful environmental contamination as the habitat corrodes over time. Existing underwater habitat designs may not include a mechanism for easily releasing the habitat from its foundation, making it difficult to recover the habitat. For example, the Aquarius Reef Base is permanently attached to its foundation which weighs 120 tonnes. The foundation is necessary in order to weigh the habitat down to the seafloor and overcome its buoyancy. Raising such a large object from depth would be an extremely complex and time-consuming operation.

[0009] [6] Deployment of the habitat presents further challenges. For example, a system that leaves deployment cables extending from the habitat to the surface, is unsafe since the deployment cables may foul propellers of passing vessels causing a hazard to navigation. Alternatively, a foundation for the habitat including its own winching gear is problematic because a winching motor left deployed underwater for long periods of time will corrode quickly, be hard to maintain, and may ultimately break. Other systems requiring deployment of additional structures to the seafloor to accomplish either operation are also undesirable since this adds complexity to the operations.

[0010] [7] Some prior art solutions have attempted to address some of these challenges. Previously deployed underwater habitats, such as SEALAB I, II, and III, Tektite I and II, Helgoland, and the Aquarius Reef Base, were each developed with a specific mission in mind and, as such, are not designed to be recovered, refitted for a new mission, and relaunched. These earlier habitats are not designed to rest on sloping or irregular seafloors. Nor do they not include separate foundations, which greatly complicates launching and recovering the habitats from the seafloor.

[0011] [8] In another example, US3466877 describes a foundation with an upper curved portion and a lower section that rests on the seafloor. The underwater habitat includes a concave portion that is placed over the upper curved portion of the foundation, enabling the habitat to be levelled with respect to a sloping seafloor. However, this design has limitations in terms of the overall size of the habitat that can be used and it does not allow for levelling on rough or irregular seafloors. This foundation also includes a winch at the foundation which will be constantly exposed to seawater and subject to corrosion.

[0012] [9] In summary, the prior art has not provided a comprehensive solution to the challenges associated with deploying, securing, levelling, and recovering underwater habitats. There remains a need for an improved system that addresses these challenges while minimizing the complexity of the deployment and recovery operations.

[0013] Summary of the Disclosure

[0014]

[0010] According to a first aspect of the disclosure, a foundation is provided for supporting an underwater habitat on the floor of a body of water. The foundation comprises at least one leg configured to engage the floor of the body of water and a foundation connection interface configured to mate with a habitat connection interface of the underwater habitat to attach the underwater habitat to the foundation.

[0015]

[0011] According to a second aspect of the disclosure, a messenger cable threading tool is provided for threading a messenger cable through a fairlead of a foundation for supporting an underwater habitat on the floor of a body of water. The tool comprises a resilient, flexible rod with a first end and a second end, a handle positioned at the first end of the rod, and a messenger cable connector positioned at either the first or second end of the rod and configured to couple to a first end of the messenger cable.

[0016]

[0012] According to a third aspect of the disclosure, a method of threading a messenger cable through a fairlead of a foundation for supporting an underwater habitat on a floor of a body of water is provided. The method comprises coupling a first end of the messenger cable to a messenger cable threading tool. The method further comprises inserting the tool through the fairlead to insert the first end of the messenger cable through the fairlead.

[0013] According to a fourth aspect of the disclosure, a messenger cable lifting tool is provided for raising an end of a messenger cable from a foundation for supporting an underwater habitat on a floor of a body of water to a surface of the body of water. The tool comprises a holder configured to hold the end of the messenger cable. The tool further comprises a handle configured to be held by at least one of a diver, a submersible arm, or a hook of a surface crane.

[0017]

[0014] According to a fifth aspect of the disclosure, a method of raising an end of a messenger cable from a foundation for supporting an underwater habitat on a floor of a body of water to a surface of the body of water is provided. The messenger cable is threaded through a fairlead of the foundation. The method comprises attaching an eye of a first messenger cable lifting tool to a crane of a surface vessel, the first messenger cable lifting tool comprising a holder holding a first end of the messenger cable extending from a first side of the fairlead. The method further comprises lifting the first messenger cable lifting tool to the surface vessel, thereby paying out the messenger cable.

[0018]

[0015] According to a sixth aspect of the disclosure, an interconnector is provided for connecting an underwater habitat to a cable via a fairlead of a foundation for supporting an underwater habitat on the floor of a body of water. The interconnector comprises a resilient, flexible rod with a first end and a second end, a first connector at the first end of the rod configured to connect to the underwater habitat, and a second connector at the second end of the rod configured to connect to an end of the cable. The first end of the rod is configured to be pushed through the fairlead to connect the first connector to the underwater habitat.

[0019]

[0016] According to a seventh aspect of the disclosure, a method of deploying an underwater habitat from a surface of a body of water to a foundation on the floor of the body of water is provided. The method comprises connecting a first end of a deployment cable to the underwater habitat, connecting a second end of the deployment cable to a surface winch, pulling the deployment cable through a fairlead of the foundation to pull the underwater habitat down to the foundation, and attaching the underwater habitat to the foundation.

[0020]

[0017] According to an eighth aspect of the disclosure, a method of recovering an underwater habitat from a foundation on the floor of a body of water to a surface of the body of water is provided. The method comprises connecting a first end of a recovery cable to the underwater habitat, connecting a second end of the recovery cable to a surface winch, unlocking the underwater habitat from the foundation, increasing buoyancy of the underwater habitat so that the underwater habitat becomes positively buoyant, and paying out the recovery cable to float the underwater habitat to the surface.

[0021]

[0018] According to a ninth aspect of the disclosure, a leg is provided for a foundation for supporting an underwater habitat on a floor of a body of water. The leg comprises a first section and a second section. The leg further comprises a length extension mechanism configured to move the second section relative to the first section to change a length of the leg.

[0022] Brief Description of the Drawings

[0023]

[0019] Examples are described in more detail below with reference to the appended drawings.

[0024]

[0020] Fig. 1(a) shows a foundation for supporting an underwater habitat on a seafloor.

[0025]

[0021] Fig. 1(b) shows another foundation for supporting an underwater habitat on a seafloor.

[0026]

[0022] Fig. 2(a) shows an underwater habitat connected to the foundation of Fig. 1(a), and Fig. 2(b) shows three underwater habitats connected to the foundation.

[0027]

[0023] Fig. 3 shows an exemplary adjustable leg of the foundation in retracted (Fig. 3(a)) and extended positions (Fig. 3(b)).

[0028]

[0024] Fig. 4 shows an alternative exemplary adjustable leg of the foundation.

[0029]

[0025] Fig. 5 shows another alternative exemplary adjustable leg of the foundation.

[0030]

[0026] Fig. 6 shows a further alternative exemplary adjustable leg of the foundation.

[0031]

[0027] Fig. 7 shows an exemplary attachment system for connecting the underwater habitat to the foundation.

[0032]

[0028] Fig. 8 shows an alternative exemplary attachment system for connecting the underwater habitat to the foundation.

[0033]

[0029] Fig. 9 shows another alternative exemplary locking system for connecting the underwater habitat to the foundation.

[0034]

[0030] Fig. 10 shows an interconnector for connecting the underwater habitat to a cable.

[0031] Fig. 11 shows a messenger cable threading tool.

[0035]

[0032] Fig. 12 shows various stages of a method of threading a messenger cable through a fairlead.

[0036]

[0033] Fig. 13 shows various stages of a method of raising the ends of messenger cable to the surface.

[0037]

[0034] Fig. 14 shows a flow chart for the method shown in fig. 13.

[0038]

[0035] Fig. 15 shows various stages of another method of raising the ends of a messenger cable to the surface.

[0039]

[0036] Fig. 16 shows a flow chart for the method shown in fig. 15.

[0040]

[0037] Fig. 17 shows various stages of a method of deploying an underwater habitat to a foundation on the seafloor.

[0041]

[0038] Fig. 18 shows a flow chart for the method shown in fig. 17.

[0042]

[0039] Fig. 19 shows various stages of a method of recovering an underwater habitat from a foundation on the seafloor.

[0043]

[0040] Fig. 20 shows a flow chart for the method shown in fig. 19.

[0044] Detailed Description

[0045]

[0041] 1. Overall configuration of a foundation for an underwater habitat

[0046]

[0042] Figs. 1(a) and 1(b) each show a foundation 100 for supporting an underwater habitat 10 on a seafloor. The foundation 100 is designed to provide a stable platform for the underwater habitat 10, and one which can support that habitat 10 in a level orientation, even where the seafloor is irregular. Moreover, the foundation 100 is designed such that it is easy to attach and detach the habitat 10 therefrom. The foundation 100 is deployable to a seafloor, but also to the floor of any body of water, such as rivers, estuaries, lakes, and reservoirs. For ease, the terminology “seafloor” is used throughout this description, but it will be understood that it refers to the floor of any body of water.

[0047]

[0043] The foundations 100 in Figs. 1(a) and 1(b) each have three adjustable legs 120, each configured to engage the seafloor. The legs 120 are connected together by a frame 110. In Fig. 1(a) a connection interface 130 is incorporated in a leg of the foundation and is designed to attach to, i.e. , lock to, a connection interface of the habitat such that the habitat is securely connected to the foundation. In Fig. 1(b) the connection interface 130 is located in on the frame 110 and / or on one or more of the legs 120.

[0048]

[0044] The frame 110 includes primary beams 112 interconnecting the legs 120. The primary beams 112 are braced and stiffened by secondary beams 114. The legs 120 are arranged at corners of a triangle and the primary beams 112 run along the edges of that triangle. The secondary beams 114 interconnect primary beams 112 on adjacent sides of the triangle. Fig. 1(a) shows a frame 110 having the form of an equilateral triangle. The primary and secondary beams are made of steel, which has a high corrosion resistance.

[0049]

[0045] Fig. 1(a) shows that each pair of legs 120 is connected by a pair of parallel primary beams 112 for increased rigidity of the overall foundation and better lateral support of each leg. As a result, the secondary beams 114 are also provided in pairs across each corner of the triangle to connect each primary beam 112 to the primary beam on the adjacent side of the triangle. It is possible to join each pair of primary beams 112 with flat plates along their length to increase the stiffness of the frame, but this presents a greater surface area to water current flow, increasing the risk of capsizing the foundation. Instead, Fig. 1(a) shows a “see-through” arrangement that presents a reduced surface area to water current flow achieved by diagonally arranged cross-struts arranged between the pairs of beams.

[0050]

[0046] The three legs 120 of the foundation 100 are adjustable, by which is meant that a length of the legs 120 can be changed. Since the legs are mutually connected by the frame 110, changing a length of the legs 120 when the foundation is resting on the seafloor changes the angle of the legs and frame, and anything attached thereto, to the horizontal. The adjustable legs allow the foundation to be levelled on irregular and sloping seafloors, providing a stable platform for the underwater habitat.

[0051]

[0047] Figs. 1(a) and 1(b) show that each leg 120 comprises a first, upper section 140 and a second, lower section 160. The two sections are slidable with respect to each other such that the length of the leg can be changed. The second section 160 is configured to engage the seafloor and the first section 140 is attached to the frame 110. In the embodiments shown in Figs. 1(a) and 1(b), a leg length extension mechanism that effects the relative sliding is housed within each leg and is not visible.

[0052]

[0048] The foundations 100 shown in Figs. 1(a) and 1(b) have three legs 120, which is favoured since a structure having three points of contact with a surface will always rest on that surface without rocking, unlike a structure with four points of contact. However, the foundation may include increased numbers of legs, depending on need, for example the number and size of habitats the foundation is intended to support. In addition, whilst each of the legs 120 shown in Figs. 1(a) and 1(b) is adjustable to provide maximum levelling capability and redundancy in case one of the leg length extension mechanisms fails, variants of the foundation are contemplated where none of the legs are adjustable, one of the legs is adjustable, or two of the legs are adjustable. If the foundation is to have levelling capabilities, at least two of the legs must be adjustable.

[0053]

[0049] The legs 120 the foundation 100 engage the seafloor in one or more of a variety of possible ways. For example, the lower sections 160 may each comprise a pile configured to be driven into the seafloor, a foot configured to rest on a surface of the seafloor, a suction caissons configured to hold on to the seafloor via suction, or an anchor.

[0054]

[0050] If needed, the foundation 100 can be equipped with ballast to weigh the foundation 100 down to the seafloor and overcome the buoyancy of an attached habitat.

[0055]

[0051] Fig. 1(a) shows a foundation connection interface 130 positioned at the top of each of the legs 130. In other examples, a connection interface 130 can be positioned on any surface of the foundation accessible from above, such as on the frame as shown in Fig. 1(b). Moreover, only a single connection interface 130 need be provided, for example if it is intended only to connect a single habitat 10 to the foundation 100, as shown in Fig. 2(a). Alternatively, multiple connection interfaces 130 can be provided, for example, if multiple habitats 10 are to be connected to the foundation 100, as shown in Fig. 2(b).

[0056]

[0052] Each foundation connection interface 130 interacts with the habitat connection interface to bias, i.e., push, the two interfaces towards each other when connected. In other words, the foundation connection interface 130 engages and applies a force to the habitat connection interface to pull the habitat towards the foundation. This ensures a secure, stable connection between the habitat and the foundation.

[0057]

[0053] Each foundation connection interface 130 is designed to lock releasably with the habitat connection interface of the underwater habitat 10. Locking the habitat 10 to the foundation 100 means that the habitat cannot be moved relative to the foundation so that the habitat is securely held to the foundation and cannot come loose. A releasable connection allows for easy attachment and detachment of the underwater habitat from the foundation. Various attachment systems used to connect the underwater habitat are described below. These attachment systems provide secure and reliable connections between the underwater habitat and the foundation while allowing for easy detachment when necessary.

[0054] The foundation 100 also comprises a fairlead through which a deployment cable for the underwater habitat can be routed. Fig. 3 shows a fairlead in the form of a J-tube 144 in a leg of the foundation. The fairlead can, alternatively, be a pulley (also termed “a block”). The J-tube is more robust than the pulley and not vulnerable to corrosion and seizing since there are no moving parts.

[0058]

[0055] The fairlead is positioned to direct the deployment cable through the connection interface 130. As a result, when one end of the deployment cable is attached to the connection interface of the habitat 10, and the cable is pulled through the fairlead, the habitat is pulled down to the foundation connection interface 130. This effectively automatically aligns the connection interfaces, facilitating easy attachment of the habitat to the foundation. This automatic alignment reduces or avoid the need for additional seabed winching points, components (for example, thrusters temporarily attached to the habitat) or submersibles (which may, in any case, lack sufficient power to move the habitat) to assist alignment of the connecting parts of the foundation and the habitat. Each end of the fairlead 144 can be equipped with a funnel 145a, 145b (see Fig. 12) to direct cables and other tools into and through the fairlead 144.

[0059]

[0056] In one alternative configuration, the foundation 100 comprises only a single leg 120, the leg including the foundation connection interface 130 and the fairlead. The leg includes a pile configured to be driven into the seafloor so as to hold the leg vertically upright.

[0060]

[0057] The foundation 100 provides several advantages. Firstly, the adjustable legs 120 provide ability to level the foundation on irregular and sloping seafloors. Secondly, the foundation connection interface 130 provides a secure and reliable attachment to the underwater habitat whilst still allowing the habitat to be quickly and easily detached from the foundation to facilitate easy recovery to the water’s surface. Thirdly, the fairlead provided in the foundation that directs the deployment cable through the foundation connection interface 130 facilitates easy alignment of the connecting parts of the foundation and habitat, simplifying deployment.

[0061]

[0058] 2. Adjustable Leg Mechanisms

[0062]

[0059] The leg length extension mechanisms allow for the adjustment of the length of the legs to accommodate irregularities and slopes on the seafloor, ensuring that the underwater habitat is level to the horizontal. Moreover, the mechanisms described below can be adjusted after deployment of the habitat, so the foundation and habitat can be levelled in the event of subsidence or scour of the seafloor during a mission moving the habitat out of level. In this section, various adjustable leg mechanisms are described, including a screwjack mechanism, a linear actuator mechanism, and a chain lift mechanism. Further alternative mechanisms are possible, for example ratchet / pawl or wormdrive based systems.

[0063]

[0060] 2.1. Screwjack Mechanism

[0064]

[0061] Fig. 3 shows a leg length extension mechanism comprising a screwjack mechanism. Fig. 3(a) shows the leg 120 in a retracted position and Fig. 3(b) shows the leg 120 in an extended position.

[0065]

[0062] The first leg section 140 includes an upper tubular segment 142 and a lower tubular segment 150. The upper and lower tubular segments together slidably receive the second leg section 160 in an internal volume 148 of the first leg section 140. The upper and lower tubular segments are bolted together. However, they could alternatively be joined by welding. An internal surface of the lower tubular segment 150 includes a pair of bearings 152 that slidably hold the second leg section 160. The bearings are water lubricated polymer bearings. Using a pair of bearings 152 arranged along the axis of the first leg section 140 constrains the second leg section 160 to slide along the axis.

[0066]

[0063] Providing the bearings 152 in a separate segment to the rest of the upper section 140 of the leg 120 simplifies the overall machining requirements for upper section 140, especially where the lower tubular segment 150 is short in comparison to the upper tubular segment 142. This is because the bearings 152 are machined after fabrication of the tubular segments to ensure alignment of each pair of bearings and employing a separate segment, especially one as short as possible, facilitates access to the workpiece by a machining tool (and increases the range of tools that can be used). In an alternative arrangement, instead of separate upper and lower tubular segments, the first leg section is made of a single tubular segment.

[0067]

[0064] In an alternative example, the second leg section 160 has a larger diameter than the first leg section 140 such that the first leg section 140 is slidable within an interior volume of the second leg section 160.

[0068]

[0065] The upper tubular segment 142 houses the foundation connection interface 130 and a J-tube 144, which acts as a fairlead for a deployment cable, as discussed above.

[0066] Components of the screwjack mechanism are split across the first and second sections 140, 160 of the leg 120. The upper tubular segment 142 also houses a screw 146 driven by drive input in the form of a standard Remotely Operated Vehicle (ROV) torque bucket 147. The screw 146 is made of Duplex stainless steel, which is suitable for longterm exposure to seawater. SuperDuplex 2507, or S355 with Inconel cladding are particular examples. The second leg section 160 includes a nut 162 operably connected to the screw 146. The nut 162 is made of aluminium or bronze which are also suitable for long term exposure to seawater. Alternatively, the nut 162 is made of the same material as the screw 146 reduce galvanic corrosion.

[0069]

[0067] In the present embodiment, the nut 162 is fixed relative to the bulk of the second leg section 160. The screw 146 is able to rotate relative to the first leg section 140, but is fixed vertically relative to the first leg section 140. As a result, when the screw 146 is caused to rotate upon actuation by the ROV torque bucket 147, the nut is caused to move along the screw thereby causing relative sliding movement of the first and second leg sections 140, 160 and extending or reducing the length of the leg 120. The screwjack mechanism provides a simple and reliable means of adjusting the length of the leg, allowing for precise levelling of the foundation on the seafloor.

[0070]

[0068] In an alternative arrangement, the screw 146 can be housed by the second leg section 160 and the nut 162 can be housed by the upper leg section 140. In this case, the screw 146 is rotationally fixed relative to the bulk of the second leg section 160 and the nut 162 is caused to rotate, thereby changing the length of the leg 120. In a further alternative the drive input, in this case the ROV torque bucket 147, can be housed by the lower leg section 160.

[0071]

[0069] As already explained, the screwjack mechanism is actuated by a standard ROV torque bucket 147. An ROV torque bucket is a standardised fitting used in the marine industry that can be rotationally actuated by a corresponding tool attached to an ROV or other submersible craft, or even a handheld tool held by a diver. Alternatively or additionally, other forms of drive input fittings for the screwjack mechanism can be used. For example, a simple hexagonal bolt head could be used. Using a drive input fitting that is actuated by a tool separate from the foundation means that the foundation does not need to include a motor to extend the leg, which would increase the complexity of the design and render the foundation more vulnerable to failure underwater than foundations without motors. In particular, having been deployed for several years, the motor may not work if an adjustment is required after that time.

[0070] The ROV torque bucket 147, or other drive input, is accessible from the outside of the leg so that it can be engaged by a tool, even when a habitat 10 is attached to the connection interface 130. Alternatively, the drive input fitting can be arranged at the base of the connection interface 130 to receive an input from a tool attached to the bottom of the habitat.

[0072]

[0071] It is advantageous to have multiple drive input fittings to actuate the screwjack mechanism (or the alternative length extension mechanisms described below) such that there is redundancy in the system in case one of the input devices becomes inoperable.

[0073]

[0072] In some examples, the drive input does include a motor. An advantage of using a motor is that it is the leg length can be adjusted without deploying an ROV.

[0074]

[0073] The internal volume 148 of the first leg section 140 houses the screw 146 and the nut 162. The internal volume is filled with gas, generally nitrogen. Housing the threaded components within this gas pocket prevents them being exposed to seawater, marine growth and silt. This reduces the chances of the working components of the mechanism corroding and seizing even if they have been designed for subsea use, thereby preventing the length of the leg being changed. A gas supply (not shown) is connected to the gas pocket to maintain the gas pocket during operation.

[0075]

[0074] The screwjack mechanism provides a simple and reliable means of adjusting the length of the leg, allowing for precise levelling of the foundation on the seafloor.

[0076]

[0075] Fig. 4 shows an alternative exemplary adjustable leg 120 of the foundation using a screwjack mechanism. Many of the features are the same and so these are not described in detail. The first leg section 140 includes upper tubular segment 142 and an alternative lower tubular segment 154. The upper and lower tubular segments together slidably receive a first column 171 of an alternative second leg section 170 in an internal volume 148 of the first leg section 140. An outer surface of the lower tubular segment 154 includes bearings 156 to slidably receive second columns 174 of the second leg section 170. The second columns 174 act as guideposts along which the first leg section 140 can slide. The first leg section 140 houses the same J-tube 144 connection interface 130 as in Fig. 3. The screwjack mechanism, housed within a gas pocket, is the same as that described in connection with Fig. 3. The first column 171 of the second leg section 170 includes a nut 172 operably connected to the screw 146 of the first leg section. The screw 146 is driven by the standard ROV torque bucket.

[0076] 2.2. Linear Actuator Mechanism

[0077]

[0077] Fig. 5 shows a leg 220 with an alternative leg length extension mechanism comprising a linear actuator 245. With the exception of the leg length extension mechanism, the features of the leg 220 are the same as described previously and are not described in detail.

[0078]

[0078] The linear actuator 245 has a first end connected to the first section 140 and a second end connected to the second section 160 of the leg. In particular, linear actuator 245 is housed within the first and second sections 140, 160 and the first end of the linear actuator 245 is connected to a support 246 in the first leg section 140 and the second end of the linear actuator 245 is connected to a support 262 inside the second leg section 160 and arranged vertically below the support 246. Increasing the length of the linear actuator 245 pushes the supports 246, 262 apart, thereby extending the leg 220. Reducing the length of the linear actuator 245 has the opposite result. The linear actuator mechanism provides a compact and efficient means of adjusting the leg length, allowing for precise levelling of the foundation on the seafloor.

[0079]

[0079] In an alternative configuration, the linear actuator 245 may be arranged outside the second leg section 160 and inside the first leg section 140. The end of linear actuator 245 connected to the second leg section 160 is, therefore, connected to an outer surface of the second leg section 160. In this configuration it is also possible that the point of connection to the first leg section 240 is located below the point of connection to the second section 160 such that extending the leg 220 is achieved by reducing the length of the linear actuator 245.

[0080]

[0080] The linear actuator 245 is a hydraulic leg with fresh or saltwater hydraulics. This is preferred to an oil-based system due to the reduced contamination risk in the event of failure. However, an oil-based system may be employed. Like the screwjack mechanism, the linear actuator 245 is at least partially housed in a gas pocket.

[0081]

[0081] As with the screwjack mechanism, the linear actuator 245 includes a drive input actuated by a diver or a tool separate from the foundation, such as a remotely operated vehicle (ROV) or a submersible, for example, via a standard ROV torque bucket. This allows for easy and efficient adjustment of the leg length via a mechanism that is also rugged since no motor is required. Alternatively, the linear actuator 245 can be actuated by a motor.

[0082] 2.3. Chain Lift Mechanism

[0082]

[0083] Fig. 6 shows a leg 320 with an alternative leg length extension mechanism comprising a chain lift mechanism. With the exception of the leg length extension mechanism, the features of the leg 320 are the same as described previously and are not described in detail.

[0083]

[0084] The chain lift mechanism includes a chain 343 having an end fixedly, i.e. , immovably, connected to the second leg section 160, and a windlass mounted on the first leg section 140 and operably engaged with the chain. The windlass is configured to wind in the chain to extend the leg. The chain lift mechanism provides a robust and reliable means of adjusting the length of the leg, allowing for precise levelling of the foundation on the seafloor.

[0084]

[0085] In more detail, a first end of the chain 343 is fixedly connected to an upper part 344 of the second leg section 160. The chain 343 is routed through a first block 345 at a lower end of the first leg section 140, then around a winch or windlass 346 before being directed by a second block 347 into a hollow interior of the second leg section 160. Storing the second, loose end of the chain within the hollow interior of the second leg section 160 provides a compact and efficient design for the chain lift mechanism. The winch is located in an upper portion of the first leg section 140 so that it is more easily accessible to actuate.

[0085]

[0086] As with the screwjack mechanism, the chain lift mechanism includes a drive input actuated by a diver or a tool separate from the foundation, such as a remotely operated vehicle (ROV) or a submersible, for example, via a standard ROV torque bucket. This allows for easy and efficient adjustment of the leg length via a mechanism that is also rugged since no motor is required. Alternatively, the windlass can be actuated by a motor.

[0086]

[0087] 3. Attachment Systems for Connecting Underwater Habitat to Foundation

[0087]

[0088] This section describes various attachment systems for connecting an underwater habitat to a foundation. The attachment systems each comprise a foundation connection interface on the habitat and a habitat connection interface on the habitat. These attachment systems are designed to provide a secure and stable connection between the underwater habitat and the foundation, while also being releasable to that the habitat can easily be recovered. Further alternatives are possible. For example, the habitat may have a length of chain attached thereto (used for attachment to a deployment cable) and the foundation can include a chain stopper within the fairlead such that, once the chain has been received in the fairlead on deployment, the chain stopper can be engaged to anchor the habitat to the foundation.

[0088]

[0089] 3.1. Pipe Clamp System

[0089]

[0090] Fig. 7 shows an exemplary attachment system for connecting the underwater habitat to the foundation. This attachment system is based on a clamp gripping a radially outwardly protruding flange.

[0090]

[0091] The foundation connection interface 130 is formed in the upper part of the first leg section 140, which is cylindrical in section. The uppermost edge of the first leg section 140 is formed into a first radially outwardly protruding flange 132. The connection interface 30 of the habitat 10, to which the foundation interface is configured to connect, includes a second radially outwardly protruding flange 32. The pair of flanges share a common diameter so that the second flange 32 can abut against and rest on top of the first flange 132 when the habitat 10 is joined to the foundation 100.

[0091]

[0092] The habitat connection interface further includes a clamp 33. The clamp includes a pair of clamp pads 36, 37. Viewed from above, each clamp pad is a portion of an annulus having a radius approximately equal to that of the flanges. In vertical cross-section, the clamp pads 36, 37 are U-shaped so as to receive the flanges therein. The clamp pads 36, 37 are connected together for relative movement around a circle thereby defining a clamp 33 having a controllable circumference / diameter. For example, ends of the clamp pads 36, 37 can be connected by a screw thread, which can be actuated to reduce or increase the circumference of the clamp 33. An alternative way of looking at this movement is that the diameter between the opposing clamp pads 36, 37 is reduced or increased. The clamp pads 36, 37 are actuated to be moved towards and away from each other to lock and unlock the clamp. In an unlocked position of the clamp 33, its circumference is sufficiently large it can pass over the flanges 32, 132. In other words, in the unlocked position, the clamp pads 36, 37 are positioned sufficiently far apart that they can move past the flanges 32, 132. In a locked position, the circumference of the clamp 33 is reduced to tighten the clamp pads onto the flanges to thereby lock the habitat 10 to the foundation 100. In other words, the clamp pads 36, 37 are moved towards each other to grip the flanges 32, 132.

[0092]

[0093] The opposing inside faces of the U-shaped clamp pads 36, 37 are angled slightly towards each other towards the base of the “U”. Correspondingly, the upper face of the flange 32 and the lower face of the flange 132, i.e., the surfaces of the flanges that do not abut together, are angled such that the flanges reduce in thickness towards their radially outer edges. As a result, when the clamp pads 36, 37 are tightened onto the flanges, the angled surfaces interact such that the U-shaped clamp pads 36, 37 push the flanges 32, 132 towards each other. Advantageously, this biases the habitat and the foundation 100 towards each other, thereby ensuring a strong, stable connection between them.

[0093]

[0094] As with the leg length extension mechanisms, the clamp 33 includes a drive input to control the clamp pads 36, 37. The drive input is actuated by a diver or a tool separate from the foundation, such as a remotely operated vehicle (ROV) or a submersible, for example, via a standard ROV torque bucket 38. This allows for easy and efficient locking and unlocking of the habitat to the foundation. The system is also rugged since no motor is required. Alternatively, the linear actuator 245 can be actuated by a motor, which avoids the need for deployment of an ROV or other submersible.

[0094]

[0095] A particular advantage of this system is that the moving parts are located on the outside of the structure, enabling easy access for repair and maintenance.

[0095]

[0096] The connection interfaces also include features to assist translationally and rotationally align the interfaces. Such features facilitate deployment of the habitat 10 to the foundation since by correcting small misalignments without requiring a submersible, which may find the task challenging. This increases the speed with which a deployment can be accomplished. The alignment features described below in connection with the pipe clamp can also be employed in connection with the other attachment systems described herein.

[0096]

[0097] Fig. 7, shows that that inner surface of the first flange 132 includes a first angled surface 134. The first angled surface 134 is angled radially outwardly from the vertical around the rim of the foundation connection interface 130. The habitat connection interface 30 includes second angled surface 34, again angled radially outwardly. As a result, when the habitat is lowered onto the foundation, the first and second angled surfaces 34, 134 interact to correct any translational misalignment of the connection interfaces. The second angled surface is formed as an inverted frustrum of a cone. The first and second angled surfaces 34, 134 effectively form a translational alignment system. It will be appreciated, that the translational alignment system will still function in the absence of the first angled surface 34 since the second angled surface 134 would still interact with the inside edge of the flange 32.

[0097]

[0098] The foundation connection interface also includes a radially inwardly protruding guide feature or protrusion 136 on an inner surface of the first leg section 140. Correspondingly, the habitat connection interface includes a slot 35 in a surface of the inverted frustrum of the cone. The slot 35 is sized to receive the guide feature 136. The sides of the slot 35 taper inwardly towards the top of the slot. In other words, the slides are the slot are angled circumferentially. As a result, when the habitat is lowered onto the foundation, the guide feature 136 and the slot 35 interact to correct any rotational misalignment of the connection interfaces. Thus, the guide feature 136 and the slot 35 form a rotational alignment system.

[0098]

[0099] Whilst the clamp 33 described above is part of the habitat connection interface 30, it can equally be comprised by the foundation connection interface 130. In addition, whilst a pair of flanges is described, it is only necessary to have a single flange comprised by the interface opposite to that which comprises the clamp 33. Moreover, whilst the connection interface 130 is described as being formed as part of a leg 120, it could equally be mounted on the frame 110.

[0099]

[0100] 3.2. Male and Female Socket Connector System

[0100]

[0101] Alternatively, the attachment system for connecting the underwater habitat to the foundation comprises a male and female socket connector system. An example of such a connector system is Enginuity’s SEAStab connection system. In this system, the foundation connection interface comprises one of a male or female socket connector, and the habitat connection interface comprises the other of a male and female socket connector. The female connector is configured to receive and lock to the male connector in order to attach the underwater habitat to the foundation. The connectors can be designed to releasably lock to each other. A male / female connection system provides a simple and secure means of connecting the underwater habitat to the foundation, whilst also facilitating recovery of the habitat from the foundation.

[0101]

[0102] The same translational and rotational alignment system discussed above in connection with the pipe clamp attachment system can be used with the male / female attachment system.

[0102]

[0103] 3.3. Locking Pin and Receptacle System

[0103]

[0104] Fig. 8 shows an alternative attachment system for connecting the underwater habitat to the foundation. A second connection interface 40 of the underwater habitat 10 comprises three radially extending locking pins 44 configured to be received by corresponding pin holes or receptacles 138 in the first connection interface 130. Only one of the pins is shown in Fig. 8. In practice, more or fewer pins can be employed.

[0104]

[0105] The locking pins 44 are translated into the receptacles to lock the habitat to the foundation 100. Alternatively, the pins could be rotated into receptacles 138. The pins 44 are then retracted to unlock the habitat from the foundation. An upper surface 45 of the outer end of each locking pin is angled and configured to engage an angled surface 139 of the receptacle. The interaction biases the habitat and the foundation 100 towards each, thereby ensuring a strong, stable connection between them.

[0105]

[0106] The actuation mechanism for the locking pins is not shown. A variety of mechanisms are possible. For example, each pin can be actuated by its own linear actuator. Alternatively, the pins can be attached together by a rocker bar and actuated by a single linear actuator, motor, or drive input such as a standard ROV torque bucket.

[0106] Alternatively, the pins could be biased into the extended, i.e. , locking position, by a resilient biasing member such as a spring.

[0107]

[0107] As discussed above in connection with the pipe clamp attachment system, the habitat connection interface 40 includes an inverted frustrum of a cone 42 to facilitate translation alignment with the foundation connection interface 130, via the first angled surface 134 thereof. Whilst not shown in Fig. 8, the same rotational alignment system as discussed in connection with Fig. 7 can be employed. Alternatively, the locking pins 44 can interact with guide slots in the foundation connection interface to achieve the same result.

[0108]

[0108] 3.4 Locking Lug and Locking Ring System

[0109]

[0109] Fig. 9 shows another alternative attachment system for connecting the underwater habitat 10 to the foundation 100. The habitat connection interface 50 comprises locking lugs 52 shaped as pins. The locking lugs 52 protrude outwardly from the surface of the habitat connection interface 50. The habitat connection interface 230 includes slots 236 arranged to receive the locking lugs. The upper edges of the slots are tapered and include circumferentially angled guide surfaces 234. These surfaces 234 interact with the locking lugs 52 to rotationally align the habitat connection interface with the foundation connection interface 230 in the same manner as described above in connection with the pipe clamp.

[0110]

[0110] The habitat connection interface 230 also includes a locking ring 238. The locking ring is rotatable with respect to the walls of the interface. The locking ring 238 includes holes 239 or gaps through which the locking lugs 52 are able to pass when the locking ring 238 is in an unlocked position where the holes 239 are aligned with the slots 236. The locking ring 238 is rotatable into a locked position where the holes 239 are moved out of alignment with the slots 236, thereby capturing the locking lugs 52 beneath the ring and locking the habitat 10 to the foundation 100. Moreover, the lower surface of the locking ring adjacent each of holes 239 is angled such that a vertical thickness of the locking ring decreases towards the holes 239. In other words the locking ring 238 comprises ramped surfaces. The ramped surfaces ride over the locking lugs 52 such that the locking ring 238 applies a downwards force on the locking lugs 52, thereby biasing the habitat and foundation connection interfaces towards each other. This ensures a strong, stable connection between them.

[0111]

[0111] The actuation mechanism for the locking ring 238 is not shown. A variety of mechanisms are possible. For example, the locking ring 238 can be actuated by a linear actuator, motor, or drive input such as a standard ROV torque bucket. An advantage of this system is that the moving parts are located on the outside of the structure, enabling easy access for repair and maintenance.

[0112]

[0112] As discussed above in connection with the pipe clamp attachment system, the habitat connection interface 50 includes an inverted frustrum of a cone to facilitate translation alignment with the foundation connection interface 120.

[0113]

[0113] 4. Interconnector for Connecting Underwater Habitat to Cable

[0114]

[0114] Fig. 10 shows an interconnector 600 for connecting the underwater habitat to a deployment cable 90 or a recovery cable. The interconnector 600 comprises a resilient yet flexible rod 610. This rod can also be described as a semi-flexible tendon. The rod 610 is flexible enough to bend around the curve of a J-tube 144 in the foundation 100. The rod 610 is also stiff enough to be pushed through without buckling, i.e. , the rod is somewhat resilient such that held at a first end and have its second end pushed through the J-tube without buckling anywhere along the length of the rod. The rod 610 also has sufficient strength under tension to pull the habitat down to the foundation. For example the rod 610 may be constructed of a GRP (glass reinforced plastic) tube with a Dyneema (ultra-high- molecular-weight polyethylene) line running though the centre, or, alternatively, a hydraulic hose with a Dyneema line running through the centre.

[0115]

[0115] A first end of the tendon 610 comprises a first connector 614 configured to connect releasably to an underwater habitat connector 20. A second end of the tendon 610 comprises a second connector 616 configured to connect to a first end 92 of a deployment cable 90. As shown, both the first and second connections 614, 616 are male connectors, for example, male SEAStab connectors by Enginuity. It is easier to pass male connectors through the J-tube than female connectors due to their smaller diameter. The releasable connection facilitates detachment of the deployment cable after the habitat has been deployed to the seafloor so that the deployment cable is not left floating or on the seabed where it may be a hazard to navigation.

[0116]

[0116] The rod 610 has a handle 612 attached thereto. The handle is for gripping by a diver or an arm of an ROV or submersible so that the interconnector 600 can be pushed through the J-tube and connected with the habitat. The handle can be an eye configured to receive the hook of a surface crane. Alternatively, the handle can simply be an outer surface of the rod 610 which can be grasped by a diver or arm of a submersible.

[0117]

[0117] After the habitat has been connected to the foundation, the habitat connector 20 is not directly accessible since it is contained within the attached connection interfaces. Hence, when it is desired to recover the habitat from the foundation, the only way to access the habitat connector 20 is via the J-tube 144. Due to the bend in the J-tube it can be tricky to thread the deployment or recovery cable therethrough without the interconnector 600, either because these cables are heavy and hard for a diver or ROV to manipulate and connect accurately and easily to the underwater habitat, or because the bend in the J-tube causes the cables to buckle, preventing them being threaded through to the habitat. The interconnector 600 is designed to facilitate the connection of an underwater habitat to a cable, such as a deployment or recovery cable, through the J-tube 144 in the foundation 100. In particular, the interconnector 600, which is only a little longer than the J-tube (i.e. , around 1-2 m long), is easy for a diver or ROV to manipulate through the J-tube due to is small size. The interconnector 600 is also sufficiently resilient to resist buckling as it is pushed through the J-tube. In addition, the releasable connection of the interconnector 600 to the habitat means that the interconnector can be removed easily after deployment so that the interconnector is not left to corrode during the length of a mission. Such corrosion could result in failure of the interconnector during the recovery operation leading to a dangerous, uncontrolled ascent of the habitat.

[0118]

[0118] 5. Messenger Cable Threading Tool and Methods

[0119]

[0119] Fig. 11 shows a messenger cable threading tool 500 and a messenger cable 520. As will be explained in more detail below, messenger cables are often used when deploying or recovering habitats 10 from foundations 100. The messenger cables 520 are threaded through the J-tubes 144. If there is no other cable already positioned in the J- tube, the messenger cable needs to be threaded through by pushing. Because messenger cables are generally light lines made of rope, for example, 10 mm dyneema, they have a tendency to buckle during the threading process. The messenger cable threading tool 500 is designed to thread the cable through efficiently and without buckling. This increases the speed and efficiency of the deployment and recovery operations.

[0120]

[0120] The tool 500 includes a resilient yet flexible rod 516 and a handle at a first end of the rod in the form of an eye 515 for the hook of a crane of a surface vessel. The handle can also be configured to be held by a diver, a submersible arm, providing a convenient means for manipulating the tool during the threading process. Alternatively, the handle can simply be an outer surface of the rod 610 which can be grasped by a diver or arm of a submersible.

[0121]

[0121] The rod 516 can also be described as a semi-flexible tendon. The rod 516 is flexible enough to bend around the curve of a J-tube 144 in the foundation 100. The rod 516 is also stiff enough to be pushed through without buckling, i.e., the rod is somewhat resilient such that held at a first end and have its second end pushed through the J-tube without buckling anywhere along the length of the rod. The flexibility of the rod enables it to conform to the shape of the fairlead, while its resilience ensures that it maintains its shape and does not become permanently deformed during use so that it can accurately align with the J-tube on subsequent uses. For example the rod 610 may be constructed of a GRP tube with a Dyneema (ultra-high-molecular-weight polyethylene) line running though the centre, or, alternatively, a hydraulic hose with a Dyneema line running through the centre.

[0122]

[0122] The rod 516 in Fig. 11 is in the form of a hollow pipe through which the messenger cable 520 can be threaded. The diameter of the bore of the rod 516 is slightly larger than that of the messenger cable, such that a stopper knot or loop 522 can be tied in the end of the messenger cable to prevent that end of the messenger cable sliding back through the rod until the knot or loop is undone. In this way, an axial face of the second end of the rod functions as a messenger cable connector that couples the messenger cable 520 to the tool 500.

[0123]

[0123] The tool 500 includes a reel 510 at the first end of the rod 516 around which the rest of the messenger cable 520 can be wound. The reel 510 is housed within a container 512 to reduce the likelihood of the messenger cable 520 working loose from the reel 510 and fouling other features of the habitat and foundation. The container 512 either comprises rigid walls or an elasticated sock surrounding the reel to gently force the messenger cable 520 against the reel 510. The container can provide a protective enclosure for the messenger cable, shielding it from damage and preventing it from becoming tangled during the threading process. The reel and the container allow the messenger cable 520 to be paid out from the tool 500 in a controlled manner as the tool is raised to the surface after the messenger cable 520 has been threaded through the J-tube 144.

[0124]

[0124] Alternatively, the tool can comprise only one or none of the reel 510 or the container 512. In the latter case, the messenger cable is paid out from a surface station as the tool is lowered to the foundation 100.

[0125]

[0125] The tool 500 also includes ballast and guidance features 514. The ballast acts to weigh the tool 500 down so that it sinks and lowers itself into the J-tube. Thus, the tool does not require pushing into place by a diver or ROV, improving operational efficiency. The guidance features 514 include angled surfaces formed by an inverted frustrum of a cone. The guidance features 514 interact with the foundation connection interface 130 to align the tool with the foundation connection interface as it is lowered onto the foundation. In particular, the rod 516 is aligned with the J-tube. This process is further assisted by a funnel 145a at the top of the J-tube that directs the tip of the second end of the rod 516 into the J-tube. The guidance features help avoid or reduce the need for a diver or ROV to assist with aligning the tool with the J-tube and the threading operation in general. Thus, the operation is more efficient and safer.

[0126]

[0126] Fig. 12 shows various stages of a method of threading a messenger cable 520 through the J-tube 144 in the leg 120 using the tool 500. Fig. 12(a) shows the tool 500 suspended above the J-tube 144 by a surface crane or winch, for example, a crane on a surface vessel. An end of the messenger cable 520 is coupled to the end of the rod 516 and the remainder of the messenger cable is wound around the reel 510 of the tool 500. Subsequently, the messenger cable threading tool 500 is lowered by the crane onto the foundation connection interface 130, as shown in Fig. 12(b). As this happens, the guidance features 514 act to align the tool 500 with the foundation connection interface and, hence, the J-tube 144. The funnel 145a guides the tip of the rod 516 into the J-tube. The resilient nature of the rod 516 means that it is pushed through the J-tube without buckling, thereby threading the messenger cable 520 through the J-tube 144 efficiently. The end of the messenger cable 520 is then accessible at the end of the J-tube 144 and can be retrieved in a subsequent step of the operation. In addition to or instead of being lowered by a crane, the tool could be manipulated by a diver or ROV.

[0127]

[0127] Alternatively, the flexible, resilient rod 516 can be in the form of a solid rod, i.e. , without a bore and the messenger cable 520 can be tied to an eye, ring or loop at the first end of the rod. In this variant, the tool 500 does not include a reel or cable container and it is operated like a needle and threaded through the J-tube, i.e., the rod is pushed through the J-tube until the tip of the rod appears at the other end of the J-tube where it can be pulled through to thereby thread the messenger cable through the J-tube.

[0128]

[0128] 6. Messenger Cable Lifting Tool

[0129]

[0129] A messenger cable lifting tool 700 is shown in Fig. 15. The tool 700 is used for raising an end of a messenger cable 520 from a foundation 100. The messenger cable lifting tool 700 is the same as the messenger cable threading tool 500 except that it does not comprise the rod 516, the ballast, or the guidance features 514. The reel 710, container 712, and eye 715 are the same as those of the messenger cable threading tool and are not described again.

[0130]

[0130] 7.1. First Method of Raising Messenger Cable Ends to Surface

[0131]

[0131] Fig. 13 shows stages of a method of lifting the ends of a messenger cable 520 to the surface after the messenger cable has been threaded through the J-tube 144 by a messenger cable threading tool 500. A flow diagram for the method is presented in Fig. 14.

[0132]

[0132] At step S100, shown in Fig. 13(a), an ROV, submersible, or diver is used to attach a first end of the messenger cable 520 to the hook of a surface crane or winch, for example, on a surface vessel. The first end of the messenger cable 520 is subsequently lifted to the surface by the crane. The reel 510 and / or container 512 of the messenger cable threading tool 500 pays out the messenger cable 520 as the first end of the messenger cable 520 is pulled up to the surface.

[0133]

[0133] At step S110, shown in Fig. 13(b), the ROV, submersible, or diver is used to attach the surface crane to the eye 515 of the messenger cable threading tool 500. Subsequently, the crane pulls the messenger cable threading tool 500 up to the surface and the reel 510 and / or container 512 pays out the messenger cable 520 in the process. The elasticated sock of the container 512 helps control the rate at which the messenger cable 520 is paid out.

[0134] At the end of the method, both ends of the messenger cable 520 have been retrieved to the surface and the messenger cable is threaded through the J-tube 144 of the foundation.

[0134]

[0135] 7.2. Second Method of Raising Messenger Cable Ends to Surface

[0135]

[0136] Fig. 15 shows stages of a method of lifting the ends of a messenger cable 520 to the surface used, for example, when the foundation 100 has been deployed to the seafloor with the messenger cable threaded through the J-tube 144 and which each end of the messenger cable 520 stored on in a messenger cable lifting tool 700. A flow diagram for the method is presented in Fig. 16.

[0136]

[0137] At step S200, shown in Fig. 15(a), an ROV 800, submersible, or diver is used to attach an eye 715 of a first messenger cable lifting tool 700 to the hook of a surface crane or winch.

[0137]

[0138] At step S210, shown in Fig. 15(b), the first messenger cable lifting tool 700 is lifted to the surface by the crane. The reel 710 and / or container 712 of the first messenger cable lifting tool 700 pays out the messenger cable in the process. The elasticated sock of the container 712 helps control the rate at which the messenger cable 520 is paid out.

[0138]

[0139] At step S220, shown in Fig. 15(c), the ROV, submersible, or diver is used to attach the surface crane or winch to the eye 715 of a second messenger cable lifting tool 700, held in a holder 116 of the foundation. Subseguently, the crane pulls the second messenger cable lifting tool 700 up to the surface and the reel 710 and / or container 712 pays at the messenger cable 520 in the process. The elasticated sock of the container 712 helps control the rate at which the messenger cable 520 is paid out.

[0139]

[0140] At the end of the method, both ends of the messenger cable 520 have been retrieved to the surface and the messenger cable is threaded through the J-tube 144 of the foundation.

[0140]

[0141] 8. Deployment and Recovery Methods for Underwater Habitat

[0141]

[0142] This section describes various methods for deploying and recovering an underwater habitat 10 to and from a foundation 100 on the floor of a body of water. These methods involve the use of deployment and recovery cables, interconnectors, and other components to facilitate the attachment and detachment of the underwater habitat to the foundation.

[0143] 8.1. Deployment Method of Underwater Habitat

[0142]

[0144] Fig. 17 shows stages of a method of deploying a habitat 10 to a foundation 100 after both ends of the messenger cable 520 have been retrieved to the surface and the messenger cable is threaded through the J-tube 144 of the foundation. A flow diagram for the method is presented in Fig. 18. At its most basic level, the method involves connecting a first end of a deployment cable 90 to the underwater habitat 10, which is positively buoyant and floating on the water’s surface, and a second end of the deployment cable 90 to a surface winch, for example based on the shore or on a surface vessel. The deployment cable is then pulled through a fairlead of the foundation 100 using the surface winch, which pulls the underwater habitat down to the foundation. The underwater habitat is then attached to the foundation using a suitable attachment system, such as those described in Section 3. This “pull-down” approach enables a positively buoyant habitat to be deployed to the seafloor — a positively buoyant habitat can be towed on the water’s surface to the deployment location. This, in turn, enables larger habitats to be deployed since negatively buoyant habitats must be transported to deployment locations on board ships, which limits the effective size of habitats to the load bearing capabilities of a vessel and its crane(s). A corresponding advantage also applies to recovery of the habitat from the seafloor.

[0143]

[0145] At step S300, shown in Fig. 17(a), a first end of a deployment cable 90 is connected to the underwater habitat 10, which is at the surface of the body of water, and a second end of the deployment cable 90 is connected to a first end of the messenger cable 520, which is threaded through the J-tube 144. A second end of the messenger cable 520 is held at the surface. The first end of the deployment cable 90 is connected to a connector 20 of the habitat 10 via the interconnect 600. However, the deployment cable can be connected directly to the connector 20 of the habitat 10. Alternatively, the deployment cable can be connected to the connector 20 of the habitat by a length of chain.

[0144]

[0146] At step S310, shown in Fig. 17(b), the second end of the messenger cable is pulled in by a winch at the surface, for example, on the shore or on a surface vessel, to thereby pull the deployment cable 90 through the J-tube and recover the second end of the deployment cable 90 to the surface. The deployment cable 90 is then connected to the same or another winch at the surface.

[0145]

[0147] At step S320, shown in Fig. 17(c), the habitat, which is provided with positive buoyancy, is pulled down to the foundation 100 by using the winch to pull the deployment cable 90 through the J-tube 144. A combination of the positive buoyancy, the J-tube 144 directing the deployment cable through the foundation connection interface 130, and the alignment systems of the connection interfaces, serve to direct the habitat 10 onto the foundation such that the connection interfaces align without requiring assistance from an ROV or submersible.

[0146]

[0148] At step S330, shown in Fig. 17(d), the habitat 10 is locked to the foundation 100 via an attachment system, for example, one of those discussed in section 3.

[0147]

[0149] At step S340, shown in Fig. 17(e), ballast is added to the habitat 10 such that it is provided with negative buoyancy. This assists the whole system remain securely on the seabed and reduces the need for systems that prevent the whole system from floating to the surface. Ultimately, this improves the safety. Alternatively, the habitat is provided with neutral buoyancy.

[0148]

[0150] At step S350, shown in Fig. 17(f), the deployment cable 90 and interconnector 600, if used, are detached from the habitat and recovered to the surface by the surface winch. This means that unnecessary cables are removed from the water, reducing the number of hazards to navigation of other vessels. Alternatively, the interconnector can be left attached to the foundation and only the deployment cable 90 detached and recovered.

[0149]

[0151] 8.2. Recovery Method of Underwater Habitat

[0150]

[0152] Fig. 19 shows stages of a method of recovering a habitat 10 to a foundation 100. A flow diagram for the method is presented in Fig. 20. A recovery cable can be used during this operation. The recovery cable is the same or different to the deployment cable.

[0151]

[0153] At step 400, shown in Fig. 19(a), an ROV 800, submersible or diver is used to insert an interconnector connected to a recovery cable through the J-tube and into connection with the habitat 10. Alternatively, it the recovery cable is directly attached to the recovery cable.

[0152]

[0154] At step 410, shown in Fig. 19(b), the attachment system locking the habitat 10 to the foundation 100 is unlocked, thereby allowing the habitat to be lifted from the foundation in principle.

[0153]

[0155] At step 420, shown in Fig. 19(c), the habitat is de-ballasted such that it becomes positively buoyant. During this process, at least an equal amount of force is applied by a surface winch on the recovery cable to retain the habitat on the foundation safely.

[0156] At step 430, shown in Fig. 19(d), the tension applied by the surface winch on the recovery cable is reduced slightly to allow the habitat to float to the surface in a controlled fashion. The recovery cable is detached from the habitat. Once at the surface, the habitat can be lifted onto a surface vessel.

[0154]

[0157] At step 440, shown in Fig. 19(e), the first end of the recovery cable, which remains threaded through the J-tube, is attached to a messenger cable. As shown the rest of the messenger cable is contained on a messenger cable threading tool 500 or a messenger cable lifting tool 700.

[0155]

[0158] At step 450, shown in Fig. 19(f), the recovery cable is pulled through the J-tube and the messenger cable threading tool 500 or a messenger cable lifting tool 700 is simultaneously lowered by surface crane to the foundation such that the end of the messenger cable is pulled through the J-tube by the surface winch ready for a subsequent deployment and the rest of the messenger cable is safety stowed on the foundation, not floating in the water column.

[0156]

[0159] At step 460, shown in Fig. 19(g), the recovery cable is disconnected from the messenger cable and recovered to the surface by the surface winch. As a result, no cables are left in the water column posing a hazard to safe navigation.

[0157]

[0160] It will be understood that the above description of is given by way of example only and that various modifications may be made by those skilled in the art. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of this invention.

[0158] Embodiments

[0159]

[0161] The following list provides numbered embodiments of the invention and forms part of the description. These embodiments can be combined in any compatible combination beyond those expressly stated. The embodiments can also be combined with any compatible features described herein:

[0160] 1. A foundation (100) for supporting an underwater habitat (10) on a floor of a body of water comprising: at least one leg (120) configured to engage the floor of the body of water; and a foundation connection interface (130) configured to mate with a habitat connection interface of the underwater habitat to attach the underwater habitat to the foundation.

[0161] 2. The foundation according to embodiment 1 , comprising: at least three legs, each configured to engage the floor of the body of water; and a frame (110) connecting together the at least three legs.

[0162] 3. The foundation according to embodiment 2, wherein at least two of the legs each comprise: a first section (140); a second section (160); and a length extension mechanism configured to move the second section relative to the first section to change a length of the leg.

[0163] 4. The foundation according to embodiment 3, wherein the first section is configured to contain a gas pocket (148) when the foundation is on the floor of the body of water, and wherein the length extension mechanism is configured to be at least partially housed within the gas pocket.

[0164] 5. The foundation according to embodiment 4, further comprising a gas supply configured to be connected to the gas pocket.

[0165] 6. The foundation according to any of embodiments 3 to 5, wherein the length extension mechanism is configured to be actuated by a diver or a tool separate from the foundation, wherein the length extension mechanism comprises a drive input configured to receive actuation inputs from the diver or the tool.

[0166] 7. The foundation according to any one of embodiments 3 to 6, wherein the length extension mechanism comprises a screwjack comprising: a screw (146) connected one of the first section or the second section; and a nut (162) operably engaged with the screw and connected to the other of the first section or the second section, wherein one of the screw and the nut is configured to be rotated and the other of the screw and the nut is configured to be held stationary to change the length of the leg. 8. The foundation according to any one of embodiments 3 to 6, wherein the length extension mechanism comprises a linear actuator (245), wherein a first end of the linear actuator is connected to the first section and a second end of the linear actuator is connected to the second section, wherein the linear actuator is configured to change a distance between the first end and the second end to change the length of the leg.

[0167] 9. The foundation according to any one of embodiments 3 to 6, wherein the length extension mechanism comprises a chain lift comprising: a chain having a first end fixedly connected to the second section; and a windlass mounted on the first section and operably engaged with the chain, wherein the windlass is configured to wind in the chain to extend the leg.

[0168] 10. The foundation according to embodiments 9, wherein the second section is hollow and is configured to contain a second end of the chain.

[0169] 11. The foundation according to any one of embodiments 3 to 10, wherein the first section and second section together comprise a pair of telescopic tubes, one slidable inside the other on one or more bearings (152).

[0170] 12. The foundation according to any one of embodiments 3 to 10, wherein the second section comprises a plurality of guide rails (174) and wherein the first section comprises a plurality of bearings (156) configured to slide along the guide rails.

[0171] 13. The foundation according to any one of embodiments 1 to 12, wherein the foundation connection interface is configured to mate with the habitat connection interface of the underwater habitat to attach releasably the underwater habitat to the foundation.

[0172] 14. The foundation according to embodiment 13, wherein the foundation connection interface is configured to mate with the habitat connection interface to lock the underwater habitat to the foundation.

[0173] 15. The foundation according to embodiment 14, wherein the foundation connection interface comprises a first part of a locking mechanism and the habitat connection interface comprises a second part of the locking mechanism, wherein the first part of the locking mechanism is configured to engage the second part of the locking mechanism whilst in a locked configuration such that the foundation connection interface and the habitat connection interface cannot be detached and moved relative to each other, and wherein the first part of the locking mechanism is configured to disengage from the second part of the locking mechanism whilst in an unlocked configuration such that the foundation connection interface and the habitat connection interface can be detached and moved relative to each other.

[0174] 16. The foundation according to embodiment 14 or embodiment 15, wherein the foundation connection interface is configured to bias the habitat connection interface into engagement with the foundation.

[0175] 17. The foundation according to any one of embodiments 1 to 16, wherein one of the foundation connection interface and the habitat connection interface comprises a radially outwardly protruding flange and the other of the foundation connection interface and the habitat connection interface comprises a clamp configured to engage the flange when in a locked configuration to attach the underwater habitat to the foundation.

[0176] 18. The foundation according to embodiments 17, wherein the clamp is configured to transition from an unlocked configuration, where the flange is disengaged by the clamp, to the locked configuration.

[0177] 19. The foundation according to embodiments 18, wherein the clamp comprises a first internal diameter when in the locked configuration and comprises a second internal diameter, larger than the first internal diameter, when in the unlocked configuration.

[0178] 20. The foundation according to any one of embodiments 17 to 19, wherein both the foundation connection interface and the habitat connection interface comprise a radially outwardly protruding flange and the clamp is configured to engage both flanges when in the locked configuration.

[0179] 21 . The foundation according to any one of embodiments 17 to 20, wherein the clamp is configured to be actuated by a diver or a tool separate from the foundation, wherein the clamp comprises a drive input configured to receive actuation inputs from the diver or the tool.

[0180] 22. The foundation according to any one of embodiments 17 to 21 , wherein the clamp comprises a motor configured to actuate the clamp.

[0181] 23. The foundation according to any one of embodiments 1 to 16, wherein the foundation connection interface comprises one of a male and female socket connector and the habitat connection interface comprises the other of a male and female socket connector, wherein the male and female socket connectors are configured to be connected together to attach the underwater habitat to the foundation.

[0182] 24. The foundation according to any one of embodiments 1 to 16, wherein one of the foundation connection interface and the habitat connection interface comprises at least one locking pin, wherein the other of the foundation connection interface and the habitat connection interface comprises at least one receptacle configured to receive the at least one locking pin, wherein the at least one locking pin is configured to be inserted into the at least one receptacle to attach the underwater habitat to the foundation.

[0183] 25. The foundation according to embodiment 24, wherein the at least one locking pin is translated or rotated into the at least one receptacle.

[0184] 26. The foundation according to embodiment 24 or embodiment 25, wherein the at least one locking pin comprises a plurality of locking pins and the at least one receptacle comprises a plurality of receptacles.

[0185] 27. The foundation according to embodiment 26, wherein either the plurality of locking pins comprises a single actuator configured insert all of the locking pins into the plurality of receptacles or the plurality of locking pins comprises a plurality of actuators, each configured to insert a respective locking pin into a respective receptacle.

[0186] 28. The foundation according to any of embodiments 1 to 16, wherein one of the foundation connection interface and the habitat connection interface comprises at least one locking lug, wherein the other of the foundation connection interface and the habitat connection interface comprises a locking ring, wherein one of the at least one locking lug and the locking ring is configured to be rotated from an unlocked configuration, where the at least one locking lug and the locking ring are disengaged, to a locked configuration, where the at least one locking lug and the locking ring are engaged with each other to attach the underwater habitat to the foundation.

[0187] 29. The foundation according to embodiment 28, wherein the locking ring comprises at least one engagement surface configured to engage the locking lug in the locked configuration, wherein the locking ring comprises at least one gap configured to allow passage of the at least one locking lug past the locking ring when in the unlocked configuration.

[0188] 30. The foundation according to embodiment 29, wherein the at least one engagement surface comprises a ramped surface configured slide over the locking lug to bias the foundation connection interface and the habitat connection interface towards each other when the locking ring is in the locked configuration.

[0189] 31 . The foundation according to any one of embodiments 1 to 30, wherein the foundation connection interface comprises a first translational alignment feature and the habitat connection interface comprises a second translational alignment feature, wherein the first and second translational alignment features are configured to interact with each other to translationally align the foundation connection interface and the habitat connection interface when the underwater habitat is lowered onto the foundation.

[0190] 32. The foundation according to embodiment 31 , wherein the first and second translational alignment features each comprise at least one radially angled surface.

[0191] 33. The foundation according to embodiment 31 or embodiment 32, wherein the first and second translational alignment features each comprise a frustrum of a cone.

[0192] 34. The foundation according to any one of embodiments 1 to 33, wherein the foundation connection interface comprises a first rotational alignment feature and the habitat connection interface comprises a second rotational alignment feature, wherein the first and second rotational alignment features are configured to interact with each other to rotationally align the foundation connection interface and the habitat connection interface when the underwater habitat is lowered onto the foundation.

[0193] 35. The foundation according to embodiment 34, wherein one of the first and second rotational alignment features comprises a protrusion and the other of the first and second rotational alignment features comprises at least one circumferentially angled surface configured to engage the protrusion.

[0194] 36. The foundation according to any one of embodiments 1 to 35, wherein the foundation connection interface is mounted on the at least one leg, or wherein the foundation comprises: at least three legs, each configured to engage the floor of the body of water; and a frame (110) connecting together the at least three legs and the foundation connection interface is mounted on the frame.

[0195] 37. The foundation according to any one of embodiments 1 to 36, wherein the foundation connection interface comprises a plurality of foundation connection interfaces. 38. The foundation according to any of embodiments 1 to 37, wherein the foundation connection interface is configured to function as the only physical point of contact between the foundation and the underwater habitat.

[0196] 39. The foundation according to any one of embodiments 1 to 38, further comprising a fairlead configured to: slidably receive a deployment cable connected to the underwater habitat; and direct the deployment cable through the foundation connection interface.

[0197] 40. The foundation according to embodiment 39, wherein the fairlead comprises a J- tube (144) or a pulley.

[0198] 41. The foundation according to embodiment 39 or embodiment 40, wherein the deployment cable is configured to pull the underwater habitat down to the foundation during deployment of the underwater habitat from a surface of the body of water to the foundation.

[0199] 42. The foundation according to any one of embodiments 39 to 41 , wherein a first end of the fairlead is configured to direct the deployment cable through the foundation connection interface and a second end of the fairlead is configured to direct the deployment cable to a surface vessel.

[0200] 43. The foundation according to any one of embodiments 39 to 42, wherein at least one end of the fairlead comprises a funnel for guiding an end of a cable into the fairlead.

[0201] 44. The foundation according to any of embodiments 2 to 42, wherein each of the at least three legs comprises: a first section (140); a second section (160); a length extension mechanism configured to translate the second section relative to the first section to change a length of the leg.

[0202] 45. A messenger cable threading tool (500) for threading a messenger cable (520) through a fairlead of a foundation (100) for supporting an underwater habitat (10) on a floor of a body of water, the tool comprising: a resilient, flexible rod (516) comprising a first end and a second end, the rod configured to be pushed through the fairlead; a handle positioned at a first end of the rod; and a messenger cable connector positioned at either the first or second end of the rod and configured to couple to a first end of the messenger cable.

[0203] 46. The tool according to embodiment 45, wherein the rod is configured to be held by the handle and pushed through the fairlead without buckling, and wherein the rod is configured to curve around a bend of the fairlead.

[0204] 47. The tool according to embodiment 45 or embodiment 46, wherein the handle is configured to be held by at least one of a diver, a submersible arm, or a hook of a surface crane.

[0205] 48. The tool according to embodiment 47, wherein the handle is an eye (515).

[0206] 49. The tool according to any one of embodiments 45 to 48, further comprising ballast (514).

[0207] 50. The tool according to any one of embodiments 45 to 49, further comprising guide surfaces configured to interact with guide surfaces of the foundation to guide the tool into alignment with the fairlead.

[0208] 51 . The tool according to any one of embodiments 45 to 50, further comprising a holder configured to hold a second end of the messenger cable.

[0209] 52. The tool according to embodiment 51 , wherein the holder comprises a reel (510) configured to receive the second end of the messenger cable wound thereabout.

[0210] 53. The tool according to embodiment 51 or embodiment 52, wherein the holder comprises a container (512) comprising an interior volume configured to house the second end of the messenger cable.

[0211] 54. The tool according to embodiment 53 when dependent on embodiment 52, wherein the container comprises an elastic tube configured to press the messenger cable against the reel.

[0212] 55. The tool according to any one of embodiments 45 to 54, wherein the messenger cable connector is positioned at the first end of the rod and wherein the tool further comprises a second handle positioned at the second end of the rod, the second handle being configured to be inserted through the fairlead and to be held by at least one of a diver, a submersible arm, or a hook of a surface crane. 56. The tool according to embodiment 55, wherein the messenger cable connector is an eye, ring, or loop configured for the first end of the messenger cable to be tied thereto.

[0213] 57. The tool according to any one of embodiments 45 to 54, wherein the messenger cable connector is positioned at the second end of the rod, and wherein the rod comprises a hollow tube configured to receive the first end of the messenger cable to be inserted therethrough.

[0214] 58. The tool according to embodiment 57, wherein the messenger cable connector comprises an axial face of the hollow tube configured to prevent passage of a loop or stopper in the messenger cable towards the first end of the rod.

[0215] 59. The tool according to any one of embodiments 45 to 58, wherein the fairlead comprises a J-tube.

[0216] 60. A method of threading a messenger cable (520) through a fairlead of a foundation (100) for supporting an underwater habitat (10) on a floor of a body of water, the method comprising: coupling a first end of the messenger cable to a messenger cable threading tool (500); and inserting the tool through the fairlead to insert the first end of the messenger cable through the fairlead.

[0217] 61 . The method according to embodiment 60, wherein the tool comprises the tool of any one of embodiments 45 to 59.

[0218] 62. The method according to embodiment 60 or embodiment 61 , further comprising raising the first end of the messenger cable to a surface of the body of water using at least one of a crane of a surface vessel, a diver, and a submersible.

[0219] 63. The method according to any one of embodiments 60 to 62, wherein inserting the tool through the fairlead comprises attaching a handle of the tool to a crane of a surface vessel and lowering a rod (516) of the tool through the fairlead.

[0220] 64. The method according to any one of embodiments 60 to 63, further comprising attaching a crane of a surface vessel to the tool and raising the tool to the surface. 65. A messenger cable lifting tool (700) for raising an end of a messenger cable (520) from a foundation (100) for supporting an underwater habitat (10) on a floor of a body of water to a surface of the body of water, the tool comprising: a holder configured to hold the end of the messenger cable; and a handle configured to be held by at least one of a diver, a submersible arm, or a hook of a surface crane.

[0221] 66. The tool according to embodiment 65, wherein the handle is an eye (515) configured to be held by the hook.

[0222] 67. The tool according to embodiment 65 or embodiment 66, wherein the holder comprises a reel (720) configured to have the end of the messenger cable wound thereabout.

[0223] 68. The tool according to any one of embodiments 65 to 67, wherein the holder comprises a container (512) comprising an interior volume configured to house the second end of the messenger cable.

[0224] 69. The tool according to embodiment 68 when dependent on embodiment 67, wherein the container comprises an elastic tube configured to press the messenger cable against the reel.

[0225] 70. A method of raising an end of a messenger cable (520) from a foundation (100) for supporting an underwater habitat (10) on a floor of a body of water to a surface of the body of water, the messenger cable threaded through a fairlead of the foundation, the method comprising: attaching an eye (710) of a first messenger cable lifting tool (700) to a crane of a surface vessel, the first messenger cable lifting tool comprising a holder holding a first end of the messenger cable extending from a first side of the fairlead; and lifting the first messenger cable lifting tool to the surface vessel, thereby paying out the messenger cable.

[0226] 71. The method of embodiment 70, further comprising: attaching an eye (710) of a second messenger cable lifting tool (700) to the crane of the surface vessel, the second messenger cable lifting tool comprising a holder holding a second end of the messenger cable extending from a second side of the fairlead; lifting the second messenger cable lifting tool to the surface vessel, thereby paying out the messenger cable.

[0227] 72. An interconnector for connecting an underwater habitat to a cable (92) via a fairlead of a foundation (100) for supporting an underwater habitat (10) on a floor of a body of water, the interconnector comprising: a resilient, flexible rod (610) comprising a first end and a second end; a first connector (614) at the first end of the rod configured to connect to the underwater habitat; and a second connector (616) at the second end of the rod configured to connect to an end of the cable, wherein the first end of the rod is configured to be pushed through the fairlead to connect the first connector to the underwater habitat.

[0228] 73. The interconnector according to embodiment 72, wherein the rod is configured to be pushed through the fairlead without buckling, and wherein the rod is configured to curve around a bend of the fairlead.

[0229] 74. The interconnector according to embodiment 72 or embodiment 73, wherein the first connector (614) is configured to connect releasably to the underwater habitat.

[0230] 75. The interconnector according to any one of embodiments 72 to 74, wherein the second connector (616) is configured to connect releasably to the end of the cable.

[0231] 76. The interconnector according to any one of embodiments 74 to 75, wherein the first and second connectors are identical.

[0232] 77. The interconnector according to any one of embodiments 72 to 76, wherein the first connector is a male connector, and wherein the underwater habitat comprises a female connector (20) configured to connect to the first connector.

[0233] 78. The interconnector according to any one of embodiments 72 to 77, wherein the second connector is a male connector, and wherein the cable comprises a female connector (92) configured to connect to the second connector.

[0234] 79. The interconnector according to any one of embodiments 72 to 78, further comprising a handle (612) configured to be held by at least one of a diver, a submersible arm, or a hook of a surface crane. 80. The interconnector according to any one of embodiments 72 to 79, wherein the fairlead is a J-tube.

[0235] 81. A method of deploying an underwater habitat (10) from a surface of a body of water to a foundation (100) on a floor of the body of water, the method comprising: connecting a first end of a deployment cable (92) to the underwater habitat; connecting a second end of the deployment cable to a surface winch; pulling, using the surface winch, the deployment cable through a fairlead of the foundation to pull the underwater habitat down to the foundation; and attaching the underwater habitat to the foundation.

[0236] 82. The method according to embodiment 81 , further comprising threading the deployment cable through the fairlead using a messenger cable prior to pulling the underwater habitat down to the foundation.

[0237] 83. The method according to embodiment 82, wherein connecting the second end of the deployment cable to the surface winch comprises: connecting a first end of the messenger cable to the second end of the deployment cable wherein the messenger cable is threaded through the fairlead; connecting a second end of the messenger cable to the surface winch; pulling, using the surface vessel, the messenger cable through the fairlead to recover the second end of the deployment cable to the surface winch for connection thereto and such that the deployment cable is threaded through the fairlead.

[0238] 84. The method according to embodiment 83, further comprising deploying the foundation to the floor with the messenger cable threaded through the fairlead or threading the messenger cable through the fairlead using a messenger cable threading tool.

[0239] 85. The method according to any one of embodiments 81 to 84, wherein connecting the first end of the deployment cable to the underwater habitat comprises connecting the first end of the deployment cable to the underwater habitat using an interconnector.

[0240] 86. The method according to any one of embodiments 81 to 85, further comprising providing positive buoyancy to the underwater habitat during pulling the deployment cable through the fairlead to pull the underwater habitat down to the foundation. 87. The method according to any one of embodiments 81 to 86, further comprising providing neutral or negative buoyancy to the underwater habitat after attaching the underwater habitat to the foundation.

[0241] 88. The method according to embodiment 87, wherein the neutral or negative buoyancy is provided by adding ballast to the underwater habitat.

[0242] 89. The method according to any one of embodiments 81 to 88, further comprising: releasing the deployment cable from the underwater habitat after attachment to the foundation; and recovering the deployment cable to the surface.

[0243] 90. The method according to any one of embodiments 81 to 89, wherein attaching the underwater habitat to the foundation comprises locking a habitat connection interface of the underwater habitat to a foundation connection interface of the foundation.

[0244] 91 . A method of recovering an underwater habitat (10) from a foundation (100) on a floor of a body of water to a surface of the body of water, the method comprising: connecting a first end of a recovery cable to the underwater habitat; connecting a second end of the recovery cable to a surface winch; unlocking the underwater habitat from the foundation; increasing buoyancy of the underwater habitat so that the underwater habitat becomes positively buoyant; and paying out the recovery cable to float the underwater habitat to the surface.

[0245] 92. The method according to embodiment 91 , further comprising connecting the first end of the recovery cable to the underwater habitat via an interconnector.

[0246] 93. The method according to any one of embodiments 91 to 92, further comprising connecting the first end of the recovery cable to a messenger cable before pulling the recovery cable to pull the messenger cable through the fairlead.

[0247] 94. The method according to embodiment 93, further comprising detaching the recovery cable and the messenger cable after pulling the messenger cable through the fairlead.

[0248] 95. The method according to any one of embodiments 91 to 94, wherein increasing buoyancy of the underwater habitat comprises removing ballast from the underwater habitat. 96. A leg for a foundation for supporting an underwater habitat (10) on a floor of a body of water, wherein the leg comprises: a first section (140); a second section (160); and a length extension mechanism configured to move the second section relative to the first section to change a length of the leg.

[0249] 97. The leg according to embodiment 96, wherein the first section is configured to contain a gas pocket (148) when the foundation is on the floor of the body of water, and wherein the length extension mechanism is configured to be at least partially housed within the gas pocket.

[0250] 98. The leg according to embodiment 97, further comprising a gas supply configured to be connected to the gas pocket.

[0251] 99. The leg according to any of embodiments 96 to 98, wherein the length extension mechanism is configured to be actuated by a diver or a tool separate from the foundation, wherein the length extension mechanism comprises a drive input configured to receive actuation inputs from the diver or the tool.

[0252] 100. The leg according to any one of embodiments 96 to 99, wherein the length extension mechanism comprises a screwjack comprising: a screw (146) connected one of the first section or the second section; and a nut (162) operably engaged with the screw and connected to the other of the first section or the second section, wherein one of the screw and the nut is configured to be rotated and the other of the screw and the nut is configured to be held stationary to change the length of the leg.

[0253] 101. The leg according to any one of embodiments 96 to 99, wherein the length extension mechanism comprises a linear actuator (245), wherein a first end of the linear actuator is connected to the first section and a second end of the linear actuator is connected to the second section, wherein the linear actuator is configured to change a distance between the first end and the second end to change the length of the leg.

[0254] 102. The leg according to any one of embodiments 96 to 99, wherein the length extension mechanism comprises a chain lift comprising: a chain having a first end fixedly connected to the second section; and a windlass mounted on the first section and operably engaged with the chain, wherein the windlass is configured to wind in the chain to extend the leg.

[0255] 103. The leg according to embodiment 102, wherein the second section is hollow and is configured to contain a second end of the chain.

[0256] 104. The leg according to any one of embodiments 96 to 103, wherein the first section and second section together comprise a pair of telescopic tubes, one slidable inside the other on one or more bearings (152).

[0257] 105. The leg according to any one of embodiments 96 to 103, wherein the second section comprises a plurality of guide rails (174) and wherein the first section comprises a plurality of bearings (156) configured to slide along the guide rails.

Claims

Claims1. A foundation (100) for supporting an underwater habitat (10) on a floor of a body of water comprising: at least one leg (120) configured to engage the floor of the body of water; and a foundation connection interface (130) configured to mate with a habitat connection interface of the underwater habitat to attach the underwater habitat to the foundation.

2. The foundation according to claim 1 , comprising: at least three legs, each configured to engage the floor of the body of water; and a frame (110) connecting together the at least three legs.

3. The foundation according to claim 2, wherein at least two of the legs each comprise: a first section (140); a second section (160); and a length extension mechanism configured to move the second section relative to the first section to change a length of the leg.

4. The foundation according to claim 3, wherein the first section is configured to contain a gas pocket (148) when the foundation is on the floor of the body of water, and wherein the length extension mechanism is configured to be at least partially housed within the gas pocket.

5. The foundation according to any of claims 3 to 4, wherein the length extension mechanism is configured to be actuated by a diver or a tool separate from the foundation, wherein the length extension mechanism comprises a drive input configured to receive actuation inputs from the diver or the tool.

6. The foundation according to any one of claims 3 to 5, wherein the length extension mechanism comprises a screwjack comprising: a screw (146) connected one of the first section or the second section; and a nut (162) operably engaged with the screw and connected to the other of the first section or the second section,wherein one of the screw and the nut is configured to be rotated and the other of the screw and the nut is configured to be held stationary to change the length of the leg.

7. The foundation according to any one of claims 3 to 5, wherein the length extension mechanism comprises a linear actuator (245), wherein a first end of the linear actuator is connected to the first section and a second end of the linear actuator is connected to the second section, wherein the linear actuator is configured to change a distance between the first end and the second end to change the length of the leg.

8. The foundation according to any one of claims 3 to 5, wherein the length extension mechanism comprises a chain lift comprising: a chain having a first end fixedly connected to the second section; and a windlass mounted on the first section and operably engaged with the chain, wherein the windlass is configured to wind in the chain to extend the leg.

9. The foundation according to any one of claims 3 to 8, wherein the first section and second section together comprise a pair of telescopic tubes, one slidable inside the other on one or more bearings (152).

10. The foundation according to any one of claims 1 to 9, wherein the foundation connection interface is configured to mate with the habitat connection interface of the underwater habitat to attach releasably the underwater habitat to the foundation.

11. The foundation according to claim 10, wherein the foundation connection interface is configured to mate with the habitat connection interface to lock the underwater habitat to the foundation.

12. The foundation according to claim 11 , wherein the foundation connection interface comprises a first part of a locking mechanism and the habitat connection interface comprises a second part of the locking mechanism, wherein the first part of the locking mechanism is configured to engage the second part of the locking mechanism whilst in a locked configuration such that the foundation connection interface and the habitat connection interface cannot be detached and moved relative to each other, and wherein the first part of the locking mechanism is configured to disengage from the second part of the locking mechanism whilst in an unlocked configuration such that the foundation connection interface and the habitat connection interface can be detached and moved relative to each other.

13. The foundation according to claim 11 or claim 12, wherein the foundation connection interface is configured to bias the habitat connection interface into engagement with the foundation.

14. The foundation according to any one of claims 1 to 13, wherein the foundation connection interface comprises a first translational alignment feature and the habitat connection interface comprises a second translational alignment feature, wherein the first and second translational alignment features are configured to interact with each other to translationally align the foundation connection interface and the habitat connection interface when the underwater habitat is lowered onto the foundation.

15. The foundation according to any one of claims 1 to 14, wherein the foundation connection interface comprises a first rotational alignment feature and the habitat connection interface comprises a second rotational alignment feature, wherein the first and second rotational alignment features are configured to interact with each other to rotationally align the foundation connection interface and the habitat connection interface when the underwater habitat is lowered onto the foundation.

16. The foundation according to any one of claims 1 to 15, further comprising a fairlead configured to: slidably receive a deployment cable connected to the underwater habitat; and direct the deployment cable through the foundation connection interface.

17. The foundation according to claim 16, wherein the fairlead comprises a J-tube (144) or a pulley.

18. The foundation according to claim 16 or claim 17, wherein the deployment cable is configured to pull the underwater habitat down to the foundation during deployment of the underwater habitat from a surface of the body of water to the foundation.

19. The foundation according to any one of claims 16 to 18, wherein a first end of the fairlead is configured to direct the deployment cable through the foundation connection interface and a second end of the fairlead is configured to direct the deployment cable to a surface vessel.

20. The foundation according to any one of claims 2 to 19, wherein each of the at least three legs comprises: a first section (140); a second section (160);a length extension mechanism configured to translate the second section relative to the first section to change a length of the leg.

21. A messenger cable threading tool (500) for threading a messenger cable (520) through a fairlead of a foundation (100) for supporting an underwater habitat (10) on a floor of a body of water, the tool comprising: a resilient, flexible rod (516) comprising a first end and a second end, the rod configured to be pushed through the fairlead; a handle positioned at a first end of the rod; and a messenger cable connector positioned at either the first or second end of the rod and configured to couple to a first end of the messenger cable.

22. The tool according to claim 21 , wherein the rod is configured to be held by the handle and pushed through the fairlead without buckling, and wherein the rod is configured to curve around a bend of the fairlead.

23. The tool according to any one of claims 21 to 22, further comprising guide surfaces configured to interact with guide surfaces of the foundation to guide the tool into alignment with the fairlead.

24. The tool according to any one of claims 21 to 23, further comprising a holder configured to hold a second end of the messenger cable.

25. The tool according to any one of claims 21 to 24, wherein the messenger cable connector is positioned at the first end of the rod and wherein the tool further comprises a second handle positioned at the second end of the rod, the second handle being configured to be inserted through the fairlead and to be held by at least one of a diver, a submersible arm, or a hook of a surface crane.

26. The tool according to any one of claims 21 to 24, wherein the messenger cable connector is positioned at the second end of the rod, and wherein the rod comprises a hollow tube configured to receive the first end of the messenger cable to be inserted therethrough.

27. A method of threading a messenger cable (520) through a fairlead of a foundation (100) for supporting an underwater habitat (10) on a floor of a body of water, the method comprising:coupling a first end of the messenger cable to a messenger cable threading tool (500); and inserting the tool through the fairlead to insert the first end of the messenger cable through the fairlead.

28. The method according to claim 27, wherein the tool comprises the tool of any one of claims 21 to 26.

29. A messenger cable lifting tool (700) for raising an end of a messenger cable (520) from a foundation (100) for supporting an underwater habitat (10) on a floor of a body of water to a surface of the body of water, the tool comprising: a holder configured to hold the end of the messenger cable; and a handle configured to be held by at least one of a diver, a submersible arm, or a hook of a surface crane.

30. A method of raising an end of a messenger cable (520) from a foundation (100) for supporting an underwater habitat (10) on a floor of a body of water to a surface of the body of water, the messenger cable threaded through a fairlead of the foundation, the method comprising: attaching an eye (710) of a first messenger cable lifting tool (700) to a crane of a surface vessel, the first messenger cable lifting tool comprising a holder holding a first end of the messenger cable extending from a first side of the fairlead; and lifting the first messenger cable lifting tool to the surface vessel, thereby paying out the messenger cable.31 . The method of claim 30, further comprising: attaching an eye (710) of a second messenger cable lifting tool (700) to the crane of the surface vessel, the second messenger cable lifting tool comprising a holder holding a second end of the messenger cable extending from a second side of the fairlead; lifting the second messenger cable lifting tool to the surface vessel, thereby paying out the messenger cable.

32. An interconnector for connecting an underwater habitat to a cable (92) via a fairlead of a foundation (100) for supporting an underwater habitat (10) on a floor of a body of water, the interconnector comprising:a resilient, flexible rod (610) comprising a first end and a second end; a first connector (614) at the first end of the rod configured to connect to the underwater habitat; and a second connector (616) at the second end of the rod configured to connect to an end of the cable, wherein the first end of the rod is configured to be pushed through the fairlead to connect the first connector to the underwater habitat.

33. The interconnector according to claim 32, wherein the rod is configured to be pushed through the fairlead without buckling, and wherein the rod is configured to curve around a bend of the fairlead.

34. The interconnector according to claim 32 or claim 33, wherein the first connector (614) is configured to connect releasably to the underwater habitat.

35. The interconnector according to any one of claims 32 to 34, wherein the second connector (616) is configured to connect releasably to the end of the cable.

36. A method of deploying an underwater habitat (10) from a surface of a body of water to a foundation (100) on a floor of the body of water, the method comprising: connecting a first end of a deployment cable (92) to the underwater habitat; connecting a second end of the deployment cable to a surface winch; pulling, using the surface winch, the deployment cable through a fairlead of the foundation to pull the underwater habitat down to the foundation; and attaching the underwater habitat to the foundation.

37. The method according to claim 36, further comprising threading the deployment cable through the fairlead using a messenger cable prior to pulling the underwater habitat down to the foundation.

38. The method according to claim 37, wherein connecting the second end of the deployment cable to the surface winch comprises: connecting a first end of the messenger cable to the second end of the deployment cable wherein the messenger cable is threaded through the fairlead;connecting a second end of the messenger cable to the surface winch; pulling, using the surface vessel, the messenger cable through the fairlead to recover the second end of the deployment cable to the surface winch for connection thereto and such that the deployment cable is threaded through the fairlead.

39. The method according to any one of claims 36 to 38, further comprising providing positive buoyancy to the underwater habitat during pulling the deployment cable through the fairlead to pull the underwater habitat down to the foundation.

40. The method according to any one of claims 36 to 39, further comprising providing neutral or negative buoyancy to the underwater habitat after attaching the underwater habitat to the foundation.

41. The method according to any one of claims 36 to 40, further comprising: releasing the deployment cable from the underwater habitat after attachment to the foundation; and recovering the deployment cable to the surface.

42. The method according to any one of claims 36 to 41 , wherein attaching the underwater habitat to the foundation comprises locking a habitat connection interface of the underwater habitat to a foundation connection interface of the foundation.

43. A method of recovering an underwater habitat (10) from a foundation (100) on a floor of a body of water to a surface of the body of water, the method comprising: connecting a first end of a recovery cable to the underwater habitat; connecting a second end of the recovery cable to a surface winch; unlocking the underwater habitat from the foundation; increasing buoyancy of the underwater habitat so that the underwater habitat becomes positively buoyant; and paying out the recovery cable to float the underwater habitat to the surface.

44. A leg for a foundation for supporting an underwater habitat (10) on a floor of a body of water, wherein the leg comprises: a first section (140); a second section (160); anda length extension mechanism configured to move the second section relative to the first section to change a length of the leg.

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