A hydro power generating system and device is configured to generate electrical power from the movement of water. The device consists of an elongated cylindrical hull to which comprises of a helical screw attached around the outer surface of a hull of the device. Movement of water over the screw causes the hull to rotate. The power created by the rotation of the hull is transferred to a generator located in the hull interior. The hull also contains water ballast tanks and a compressed air source in an air tank allowing adjusting the buoyancy of the device. The system is configured to couple adjacent devices in an array that can extend longitudinally, laterally and/or vertically via a common frame. At least a pair of counter-rotating screws is attached to a common frame, wherein the entire assembly of the system is anchored in flowing water.