The generator comprises: at least one energy capturing float (2) which is movable in response to wave motion; a reaction member (1) to be positioned below the energy capturing float; connecting lines (4a, 4b,4c,4d) for connecting the at least one energy capturing float to the reaction member and defining a spacing (D3) between the energy capturing float and the reaction member; energy convertors (3a,3b,3c,3d) for converting relative movement between the reaction member and at least one respective energy capturing float to useful energy. The generator includes depth setting means such as adjustable lines (8a,8b) connected to auxiliary floats (7a,7b) or adjustable mooring lines (9a,9b 9c,9d) securing the reaction member to the sea bed B for setting the depth (D1) of the reaction member in the sea.