A wave energy converter (WEC) 10 has a body portion 18 with a face 20 and at least one flexible membrane 16 bounding at least part of a volume of a fluid to form a variable volume cell 22. The membrane is inclined from vertical providing a flow smoothed passage for wave energy from a wave 14 to travel over the WEC whilst deforming the at least one membrane towards the body to compress the fluid. The cell(s) can be submerged or floating. The inclination of the at least one membrane assists conversion of potential and kinetic energy of the wave to pressure within the fluid. Fluid pressure within the WEC cell(s) and/or system can be optimised to suit wave and/or performance conditions.