The control objective for Wave Energy Converters (WECs) deviates significantly from the traditional reference “tracking” problem. In fact, a suitable control formulation for WECs should optimise the energy absorption from waves while observing, at the same time, the physical limitations of both the device and the actuator. Due to the irregular motion of the sea, computing an optimal control law achieving such objectives is non-trivial. This paper presents the application of a recently developed moment-based optimal control strategy for WECs, for a flap-type device. The main components of this theory are discussed, while highlighting its appealing characteristics for this energy-maximising application. In addition, numerical results are presented for both monochromatic and polychromatic wave inputs.