A numerical model is proposed to analyse the effect of waves in near-shore waters on the beach groundwater flow. The groundwater flow is modelled by Richards' equation which describes flows in variably-saturated porous media. A wave-driven boundary conditions is prescribed at the beach face. The model abilities are assessed against the results of a large-scale laboratory experiment called BARDEX II. This is a sand barrier with a lagoon whose level is controlled. The investigation of water flow rates through the barrier highlights the beach groundwater dynamics under different conditions.