Abstract: Pedal operated mechanisms are disclosed for propelling watercraft, with one embodiment of the invention comprising a modification for a canoe and a second form of the invention comprising a mechanism that can be secured to a surfboard. A novel flexible driveshaft is disclosed for transmitting power from the pedals to a propeller. A canoe can easily be modified to incorporate the first form of the invention, and the second form of the invention is easily secured to a surfboard or like craft. Both forms of the invention can be easily removed from the craft, once installed, and the craft converted back to its original use. In the case of the canoe, the invention provides for exercise of different parts of the body in different modes.