A human powered watercraft or land vehicle is described herein. A watercraft or land vehicle may have two pedals that reciprocated are in a linear or slightly curved trajectory but not a circular motion. As the two pedals are reciprocated, an output shaft is rotated in either a clockwise or counterclockwise direction when the left pedal is pushed forward or when the right pedal is pushed forward. The output shaft may be connected to a propeller of a watercraft or a land vehicle so as to propel the watercraft or land vehicle forward. The output shaft may receive rotational input through two gears mounted to the output shaft with one-way bearings that enable the output shaft to rotate in the same direction regardless of whether the left pedal or the right pedal is being pushed forward.