This work presents the MoonWEC, a new device for wave energy conversion. This new concept encompasses several working principles as the heaving point absorber, the oscillating water column and the overtopping. The development of the new WEC has been carried out through numerical modelling. Three main parts of the device have been simulated: a hollow floating structure, a central moonpool and a CALM mooring system. All the parts of the model have been coupled to obtained the general behaviour of the device under the effect of irregular sea states. The device has been designed according to the Mediterranean Sea wave climate. Its dimensioning aims to maximize the power absorption by tuning both,device and moonpool, natural periods with the identified prevailing sea states. Six mooring system configurations have been tested in order to obtain a stable, safe and yet effective behaviour. Finally, performance indicators have been drawn to assess power production in two selected locations in the Mediterranean Sea.