A system for generating electricity includes a buoyancy pump operable to convert wave motion from a body of water into mechanical energy. The buoyancy pump includes a buoyancy block that reciprocally moves in response to wave motion to pump an operating fluid that is delivered to a turbine to produce electricity. The buoyancy block is preferably sized such that a diameter of the buoyancy block is no less than about one-sixth a wavelength and no greater than about one wavelength of an average wave for a region in which the buoyancy pump is operated.