PURPOSE: To make it possible to efficiently convert dolphin motion to propulsion at the time when a man moves under water by fixing wings consisting of elastic materials which extend the front ends of the feet of the human body in water and generate buoyancy to a spring and converting the buoyancy alternately generated at both faces of the wings at the time when the human body makes dolphin motion to propulsion, thereby propelling the human body in the water.

CONSTITUTION: This underwater propulsion device is provided with a main structural part 2 which gradually reduces the section by the elastic body from a part 3 of a boot coupling at the toe to the extension part and converts the buoyancy to the propulsion while deflecting and the underwater wings 1 which generate the buoyancy. The spring of the main structural part 2 is acted and simultaneously the buoyancy generated in the wings 1 is accumulated in the spring in such a manner that an always adequate angle of elevation is obtd., by which the feet are pushed out in a progressing direction at the time of advancing while the wings 1 are vertically moved in water flow. A series of the actions resemble the propulsion mechanism of dolphins and whales and generate the propulsion. The shapes of the wing surfaces and sections are constituted in accordance with fluid dynamics and wing theory in such a manner, by which the buoyancy generated by the motion is efficiently changed to the propulsion.