The aim of the SEAREV project is to design a wave energy converter which will be economically viable for a moderate wave climate of about 20 kW/m. The energy production must be maximised while the costs must be minimised, which is a multi-objective optimisation problem. The mean annual energy production depends on the given deployment site, and also the shape of the device, because of the wave-structure interactions. The optimisation problem is a shape optimisation problem, with two objectives and several constraints. In our optimisation, there is a two layer process; one layer using genetic algorithms and the second using a gradient based method. Results of energy production with respect to displacement of the device are presented for different shapes. The main interest of this approach is that it highlights the important device parameters. From the wide range of generated shapes and corresponding results, it can be seen also that optimisation is necessary.