NOVELTY - The plant has a water turbine (13) horizontally arranged at a mast, and including an electrical generator and a vane body (11). A pair of two vanes (7) is radially arranged at the body and directed in one of two rotational directions. The body includes two segments detachably connected with each other. The body is arranged perpendicular to a center line of the mast, and the mast is centrally guided through the body. An upper part of the body is subjected by sea flow, waves and/or wind. A wind power plant, a photovoltaic system or a platform are arranged at the mast.    USE - Hydro-electric power plant e.g. tidal power plant, sea current power station and wave power plant, for use with Euler wind, gradient wind, geostrophic wind and cyclostrophic wind, and during buoyancy, salinity, tidal range, thermohalinity, heat flow and/or waves of a water body (all claimed), for converting kinetic energy into mechanical energy and the mechanical energy into electrical energy.    ADVANTAGE - The water turbine is horizontally arranged at the mast, and includes the electrical generator and the vane body, so that the power plant exhibits a technically simple structure and is universally applicable. The body includes two segments detachably connected with each other, thus enabling a modular design of the plant, so that the individual segments are economically floated in position and locally assembled and the modules and/or segments are simply and economically transported, and hence the segments are exactly positioned according to filling or evacuation of the water. The design of the plant avoids the need of special design of special ships. The vane body is arranged perpendicular to the center line of the mast, and the mast is centrally guided through the body, thus ensuring constructively simple and stable design of the plant. The wind power plant, the photovoltaic system or the platform are arranged at the mast, thus enabling functionalities of the plant in a simple manner and relatively less technical expenditure. The provision of the photovoltaic system ensures effective utilization of solar energy for electric energy production.    DESCRIPTION OF DRAWING(S) - The drawing shows a top sectional view of a water turbine.    Magnet (3)    Rotor (6)    Pair of two vanes (7)    Vane body (11)    Segment (12)    Water turbine (13)