A wave energy converter comprising: a buoyant structure which, in use, floats on water; a generator; a generator drive mechanism on board the buoyant structure, the generator drive mechanism having an rotational input drive shaft and a rotational output drive shaft; a drive member operably connected to the input drive shaft, the drive member being moveable back and forth between a first position and a second position; a biasing arrangement acting on the drive member; a submerged element which, in use, moves below the surface of the water out of phase with the buoyant structure, the drive member being attached by a tether to the submerged element; wherein, in use, when the buoyant structure encounters a wave crest, the spacing between the buoyant structure and the submerged element increases and the drive member is pulled towards the second position by the tether, and, when the buoyant structure encounters a wave trough, the spacing between the buoyant structure and the submerged element decreases and the drive member is urged towards the first position by the biasing arrangement; and, wherein the back and forth movement of the drive member between the first and second positions causes the input drive shaft to rotate and, thereby, causes the output drive shaft to rotate; wherein the submerged element defines a first and a second hydrodynamic surface respectively configured to damp the motion of the submerged structure in respective opposite first and second directions; and wherein the submerged element defines one or more selectively closable apertured portions each provided with an openable closure operable between a first, open position whereat flow of water through the aperture is freely permitted and a second, closed position whereat flow of water through the aperture is substantially occluded; characterised in that: openable closures are provided having a first opening mode being hinged to move to an open position under a hydrodynamic pressure acting in a first direction and openable closures are provided having a second opening mode being hinged to move to an open position under a hydrodynamic pressure acting in a second opposite direction. a buoyant structure which, in use, floats on water; a generator; a generator drive mechanism on board the buoyant structure, the generator drive mechanism having an rotational input drive shaft and a rotational output drive shaft; a drive member operably connected to the input drive shaft, the drive member being moveable back and forth between a first position and a second position; a biasing arrangement acting on the drive member; a submerged element which, in use, moves below the surface of the water out of phase with the buoyant structure, the drive member being attached by a tether to the submerged element; wherein, in use, when the buoyant structure encounters a wave crest, the spacing between the buoyant structure and the submerged element increases and the drive member is pulled towards the second position by the tether, and, when the buoyant structure encounters a wave trough, the spacing between the buoyant structure and the submerged element decreases and the drive member is urged towards the first position by the biasing arrangement; and, wherein the back and forth movement of the drive member between the first and second positions causes the input drive shaft to rotate and, thereby, causes the output drive shaft to rotate; wherein the submerged element defines a first and a second hydrodynamic surface respectively configured to damp the motion of the submerged structure in respective opposite first and second directions; and wherein the submerged element defines one or more selectively closable apertured portions each provided with an openable closure operable between a first, open position whereat flow of water through the aperture is freely permitted and a second, closed position whereat flow of water through the aperture is substantially occluded; characterised in that: openable closures are provided having a first opening mode being hinged to move to an open position under a hydrodynamic pressure acting in a first direction and openable closures are provided having a second opening mode being hinged to move to an open position under a hydrodynamic pressure acting in a second opposite direction.