This paper concerns the interplay between the physical geometry of a wave energy converter (WEC) and the control strategy adopted for the converter, with the ultimate aim of optimising the energy output of the device. An energy-based performance function is employed and we attempt to perform numerical optimisation of a heaving buoy employing a latching control strategy. We allow both draught and radius of the axisymmetric buoy to be adjusted using a numerical optimisation. A linear time-domain hydrodynamic program is used in order to simulate the device motion, while the optimization problem is solved by means of a simplex method. Results show the difference in the frequency response of an optimal buoy for a particular sea-state designed with and without knowledge of the control system.