NOVELTY - Turbine is located by tethers free to swing around following prevailing current direction, free to swing up and down following net forces and free to rotate in the plane of the rotors until net torque is balanced, supported by bouyancy chamber (2). The structure is only partly submerged for natural stability in the vertical operating level of turbine under different operational conditions. Bouyancy is controlled by amount of water in the bouyancy chambers.    USE - For harnessing energy from stream or river flows, or river or sea water flows or current.    ADVANTAGE - Generates energy in a sustainable way without environmental impact, such as visual intrusion of wind turbines , and with predictability of tidal, thermal or river current flows. Virtually submerged bouyancy camber isolates the structure from most effects of wave-loading, unlike in the floating structure, thus reducing loads on structure to allow more economic design. Turbine can be made bouyant and floated into position, after attachment to anchorage are ready, making installation simple and far easier. While running turbine is free to locate itself in equilibrium relative to both current direction, effects of turbulence and its imbalances which would otherwise induce considerable loads if restrained. During maintenance, bouyancy chamber and arm provide stability for structure, thus steady platform for maintenance.    DETAILED DESCRIPTION - The horizontal axis turbine (1) is supported by bouyancy chamber (2), and a restraining arm (3) which can be rigid or flexible and telescopic to accommodate turbine to different water depths. A bearing allows arm and turbine to swing and rotate in all three planes and to follow all changes in current direction. The required bouyancy may be obtained by either by powered air compressor, or by use of pre-compressed gas, or by gas released from chemical reaction or evaporation. Mechanical device may be used to in addition to or instead of bouyancy changes to move the center of gravity of the free swinging structure, e.g. by shifting of ballast.    DESCRIPTION OF DRAWING(S) - Drawing shows side view of normal operation, single rotor, rated power turbine in accordance with one embodiment of the present invention.    Turbine (1)    Bouyancy chamber (2)    Restraining arm (3)    Anchorage with bearing (4)