Abstract: An apparatus is disclosed comprising a suite of sensors for measuring instant static and dynamic pressure, speed of the water flowing past the vessel in the direction of travel of the vessel, acceleration of the vessel in the direction of motion, and position of a vessel, such as a row boat. A microprocessor receives data from the sensors and calculates power expended by the rower, paddler, or other human or non-human power source by finding the total of all forces impinging upon the vessel and passengers, thereafter multiplying by the speed of the water flowing past the vessel in the direction of travel of the vessel. In one embodiment data is stored for later analysis or for downloading to a computer or other data storage device.