The hull of the boat has a frame (2) which supports a rotatable pedal assembly (3) and a bar with fixings for the (5) two ends (1a,1b) of a drive cable (1). A frame mounted (8) at the stern supports a fin post (9) which is pivoted at the top and has a connection to the drive cable. The side of each pedal has a pulley (6) around which the cable moves with further guide pulleys (7) and reverse pulleys (10,11) further along. As the pedals rotate the rotation is translated by the pulleys into an axial motion in the cables and in turn to a swinging motion by the fin post which produces a forward hull thrust.
