A watercraft having propulsion means extending below the water line comprising a pair of flexible fins each adapted to oscillate through an arcurate path in a generally transverse direction across the central longitudinal dimension of the watercraft. As input force is applied, the fins twist to form an angle of attack for providing forward thrust while moving in both directions along the arcurate path. Each of the fins have a generally squared off top and preferably an outer area of harder rubber than the inner area. Each of the fins can be adjusted at the trailing edge to provide adjustable tensioning of the trailing edge.

A vehicle (20) consisting of a frame (22) with a pair of paddles (72) extending longitudinally and rotatably supported by the frame (22) in pendulum fashion for swinging movement between an extended position engaging the surface and a retracted position moved vertically out of engagement with the surface. A pair of foot platforms (74) are operatively connected to the paddles (72). A pair of depressors (84) interconnects the foot platforms (74) and the paddles (72) to rotate the paddles (72) between the extended position and the retracted position. The paddles (72) include a propulsion bar (86) and an oar (88) connected by a lost-motion connection to slide relative to one another between the extended position and the retracted position. The oars (88) have a fin-shape to propel the vehicle (20) over water and include a striker (90) to propel the vehicle (20) over land. The vehicle (20) allows movement over a surface of water and land using an elliptical motion similar to the natural motion of walking.

A watercraft having propulsion means extending below the water line comprising a pair of flexible fins each adapted to oscillate through an arcuate path in a generally transverse direction across the central longitudinal dimension of the watercraft. As input force is applied, the fins twist to form an angle of attack for providing forward thrust while moving in both directions along the arcurate path. Each of the fine have a generally squared off top and preferably an outer area of harder rubber than the inner area. Each of the fins can be adjusted at the trailing edge to provide adjustable tensioning of the trailing edge.