The MOONWEC, a new concept of point absorber is here presented for the first time after its patent submission. The new concept of WEC merges several working principles, with the aim to benefit from the assets of each single principle. It consists in a hollow floating structure, where the sea water fills a central whole creating a moonpool. The idea is to create a relative motion between the floater and the moonpool’s water and then, absorb the energy via a Wells turbine placed in the moonpool. The model considers the structure motion in heave, surge and pitch; the relative displacement of the moonpool, the Wells turbine rotation and its coupling to a permanent magnet generator in order to obtain the absorbed instantaneous power. Three main parts of the device have been simulated: a hollow floating structure, a central moonpool and CALM mooring system. All the parts of the model have been coupled to obtain the general behaviour of the device under the effect of irregular sea states. The paper will present the new concept and the dimensioning and optimisation of the device based on a numerical potential flow model.