A pressure differential sea wave energy converter concept using the forced harmonic motion of a hydraulic water column and hydraulic piston is presented. The mechanical power from the hydraulic piston is converted to electrical power by a linear induction generator. The equation of motion, and electrical power generated are derived in terms of design dimensions and mechanical properties of the wave energy converter. The frequency response of the system is modelled numerically for a variety of wave frequencies, and its time response is modelled using a simple Euler method numerical model. It was found that the wave energy converter yields a maximum conversion efficiency of 27% and a prompt transient response to actuation with waves around its natural frequency. High survivability and reduced visual and water-surface impact are likely advantages of this design concept, since all mechanical components may be incorporated into the sea-floor and shoreline.