Active control is a possible means of improving the cost effectiveness of wave energy devices. This paper suggests a power take-off mechanism for controlling the hydrodynamic response of a full scale oscillating water column (OWC) device. A system comprising an air turbine, a float, and a hydraulic power conversion apparatus is proposed. In order to understand the performance requirements of the mechanism, numerical investigations were carried out for the terminator and the attenuator devices. The air turbine mechanism was built in the laboratory and found to be self-starting.