A high efficiency fluid power transformer is applied generally and particularly to continuous application where efficiency gain is important, that of an underwater wave energy converter, WEC, that reciprocates as recurring waves pass over. Single acting, double acting and helical hydraulic actuators pressurize hydraulic fluid in an energy conversion system. Ultimately, the energy conversion system powers one or more hydraulic motors that drive an electric generator or multiple generators. A sensor system detects characteristics of in-coming waves or alternatively, waves in the process of wave making, such as by detecting changes in pressure as waves pass over the sensor system. The sensors can be mounted on the ocean floor a few wave lengths from the WECs, and a control computer system calculates characteristics of the waves such as wave height and speed data, and uses the data to control aspects of the WECs and components of transformer system.