Dive computers in accordance with embodiments of the invention are disclosed. One embodiment includes a microprocessor, a pressure transducer connected to the microprocessor, a microphone connected to the microprocessor, a speaker connected to the microprocessor, a telephone transceiver connected to the microprocessor, a GPS receiver connected to the microprocessor and a display. In addition, the microprocessor, pressure transducer and display are configured to display information concerning the dive computer's depth of submersion, the microprocessor, microphone, speaker and telephone transceiver are configured to enable the dive computer to be used as a telephone handset, and the microprocessor is configured to obtain GPS coordinates from the GPS receiver. In a further embodiment, the microprocessor, the microphone, the speaker, the telephone transceiver, the display, and the GPS receiver are components of a mobile phone handset including an external connector for communicating with external devices, the pressure transducer is packaged separately from the mobile phone handset and the pressure transducer packaging includes a connector configured to mate with the external connector of the mobile phone handset creating a connection between the pressure transducer and the microprocessor, and the mobile phone handset and the pressure transducer are contained within a waterproof housing. In addition, a software application installed on the mobile phone handset configures the microprocessor to record information concerning the dive computer's depth and time of submersion in a dive log.