Abstract: An apparatus configured to convert kinetic energy of water flow to electrical power. The apparatus includes an axial turbine that is designed to be submerged under a water surface and a shaft that extends from the axial turbine. The shaft is designed to extend above the water surface and provide buoyancy. The apparatus may be designed such that a waterline area of the apparatus is less than a predetermined multiplier times the displacement of the apparatus divided by the length of a wave having a low probability of occurring. In a particular case, the predetermined multiplier may be approximately five and the wave having a low probability may be a characteristic wave of approximately 3% probability. A plurality of such apparatuses may be arranged in a plurality of rows defining a system, such that an upstream apparatus does not overlap a downstream apparatus in projection to a plane transverse to the water flow.