The plane unsteady problem of a wave impact on the bow end of a catamaran wet deck is considered. The wet deck is modeled by a Euler beam. At the initial instant of time, the wave crest touches the beam edge. In order to describe the beam deflection and the liquid flow, the method of normal modes and the Wagner approach are used. The present analysis focuses on the method of treating this coupled problem and the estimations of its applicability. Preliminary numerical calculations reveal that the interaction of the beam deflection and the liquid flow may lead to hydrodynamic pressures which are higher than those for a rigid wet deck.