A pair of foils are pivotably coupled to a nacelle. The nacelle is pivotably coupled to a mast extending down from to a frame and below a water surface. A push rod oscillates, causing the nacelle to experience a heaving motion, in turn causing the foils to flap up and down. The push rod is driven by a power plant such as a human rider. Angles of attack for the foils are actively controlled to optimize lift and propulsion forces provided by the foils to cause the water craft to move over the water. A steering fin is also provided for heading control of the water craft. A control system for separate angles of attack for the foil sends appropriate information to servo motors which cause the foils to rotate relative to the nacelle to achieve optimal angles of attack relative to the particular position of the nacelle at any given moment.