A caisson breakwater module having an upwave and a downwave side and incorporating an oscillating water column, the caisson breakwater comprising a base installed on the sea bed and a lid adapted to be positioned on top of said base, the base defining a water inlet on the upwave side and further defining a water oscillation chamber, and the lid defining a breakwater section on the upwave side, a turbine chamber, one or more air ducts connected with said turbine chamber and an additional substantially sealed chamber. The invention further relates to a breakwater comprising a plurality of such modules and a lid suitable for use in such modules.