NOVELTY - The generator assembly has an impellor assembly (620) which is located in the housing (610,612) and is provided with two impellors rotating in opposite direction to each other, when in use. The two impellors are arranged such that the volume of water swept by the blades (634) of one impellor overlaps with the volume of water swept by the blades of other impellor. A flow deflector (638,640) is mounted upstream of the overlapping region of the impellors to prevent water impinging directly on the overlapping region.    USE - Generator assembly for generating energy from water in seas, oceans, river and river estuaries, for powering subsea or subterranean equipment for production of oil and gas.    ADVANTAGE - The generator can be located and operated in significant depths of water. The housing is prevented from being subjected to a twisting action or torque, and hence prevents the movement of the generator assembly out of proper alignment with the prevailing flow of water and current. The assembly is securely fixed in a place as sufficient integrity is provided. The stress applied to the retaining unit can be reduced due to the presence of buoyancy unit. The generator assembly can be operated in the highest efficiency and is not affected by the presence of any other generator assemblies in upstream. The build up of still or stagnant water moved by impellor is reduced, so that the performance of impellor assembly is improved.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a system for the generation of energy from the tidal flow of water;    (2) an installation provided with several systems;    (3) a system for generating energy from ocean water; and    (4) a subsea installation for the production of oil and/or gas.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of the generator assembly.    Housing (610,612)    Impellor assembly (620)    Blade (634)    Flow deflector (638,640)    Vane surface (650)