NOVELTY - The assembly (702) has an impellor assembly (720) located within a housing (704) and including blades (734) that are arranged to be contacted by flow of water when in use. Holding units hold the housing in an upstream orientation by the flow of water. Swept volume of adjacent impellors is overlapped. The impellors are arranged to rotate in a direction and rotate in another direction opposite to the former direction. One of the impellors is acted to prevent the assembly rotating out of an alignment with an incident current, where the units are acted upon by the flow of water.    USE - Generator assembly for generating energy e.g. electrical energy and hydraulic energy, from a flow of water or body of water e.g. rivers, river estuaries, seas and oceans, for subsea installation (claimed) for production of oil and gas at offshore locations.    ADVANTAGE - The assembly allows a buoyant unit that is provided with the generator assembly to reduce the stress applied to retaining units, and reducing wear and tear on the retaining units, and allows the retaining units with smaller dimensions and smaller cross-sections. The assembly provides connections with and between risers in a riser assembly formed in a conventional manner. The assembly provides a number and/or spacing of the assemblies to extend over any suitable depth of water so as to obtain the most efficient use of the prevailing currents. The assembly provides a tubular assembly in a conventional design to be conveniently used to form the risers to connect subsea wellhead installations with surface vessels and platforms. The assembly allows retaining assembly of sufficient length to extend from the ocean floor to a depth in which efficient operation of the assembly can be achieved.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a system for generating energy from a current flowing in a body of water    (2) a subsea installation for the production of oil and/or gas    (3) a subsea installation    (4) an impellor assembly.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of a generator assembly.    Generator assembly (702)    Housing (704)    Impellor assembly (720)    Buoyant material (730)    Blades (734)