Abstract: A basin for containing water is provided and a heavy buoyant body is guidingly received in the basin for back and forth reciprocal movement therein and also raising and lowering within the basin in response to changes in the elevation of the water level therein. One end of the basin opens toward and in opposition to a source of wave movement and the body is drivingly connected to a rotary output shaft to be driven in response to back and forth reciprocal movement of the body. The output shaft includes eccentric crankpin portions and connecting rods operably connect the reciprocal body to the crankpin portions of the output shaft. The basin opens toward the source of wave movement through a straight channel having a wave modulating gate operatively associated therewith.