An underwater turbine and generator unit 2 comprises first and second housing parts 4, 6 which define a flow channel 44, and connecting means 8 for connecting the first and second housing parts together. The connecting means 8 comprise a plurality of bars 22. The generator 2 has a base 28 having three legs 30, 32, 32. The legs 30, 32, 34 are positioned longitudinally and/or transversely outwards of the sides of the flow channel. The legs 30, 32, 34 may be provided with a skirt or flange to prevent the legs from digging into the sea or river bed.