A ship hull structure includes a main hull and a movable rearbody having an engine and a propeller. The movable rearbody is located at a lower side of a stern of the main hull, connected with an aft of the main hull to form an integral unit by a hinge linking device allowing the rearbody to pivot up and down. By a block, a crane or a winch and through a chain or a hanging wire, a pivoting angle of the movable rearbody with respect to the main hull can be adjusted and controlled. A bottom of the hull can be provided with at least one, usually plural, air cushion recess, which is filled with pressurized air to reduce a viscous force between a bottom of the ship and water. When a ship of this kind of structure is sailing, the rearbody can be lifted up by the block or the winch, allowing part of the propeller to be separated from a water surface to reduce resistance in the water that the engine can achieve a required rotational speed (RPM) in a short time. Next, the rearbody is laid down slowly, allowing the propeller to be put into the water, thereby increasing propulsion and quickly achieving a cruising speed. When the ship is sailing and encounters with wind wave, the stern will ascend by longitudinal pitching; at this time, the rearbody can descend by its own weight, with a hinge axis as a center, preventing the propeller to leave the water surface to rotate idly. On the other hand, when a bow ascends (that is, the stern descends), the rearbody will maintain a normal draught height by buoyancy of the water and the force between the water and running propeller Therefore, for the entire ship, a wetted surface area of the propeller can be adjusted automatically to keep at a best sailing condition, which can further save fuel consumption significantly. In another embodiment that the bottom of the ship is formed with the air cushion recesses, a friction force of the water can be reduced to increase a ship speed by the air cushion effect formed at the bottom of the ship.