Floating Power Plant (FPP) develops a hybrid floating wind and wave energy device. Pitching Wave Energy Converters (WECs) interact with the supporting structure, amplifying the motion of the WECs within the design wave frequency range. In this work we focus on the effect of the chamber geometry – without the WEC – in amplifying the waves inside the chamber. The simulations are carried out using two-phase Navier-Stokes simulations. We investigate the wave propagation and the interaction between waves and the fixed support structure. The simulations are compared to experimental tests performed in the wave basin at Aalborg University.