The ratios of B/Land dr/d for both regular and irregularwaves in the case of the single fixed FB have been shown to be the most important parameters. For the heave motion FB, the influence of the motion on the efficiency is examined (Fig. 8). The influence of a plate and porous plate, offering an increased local draught, is examined in the next two sets of experiments. In the last set, a double FB configuration is tested, to reveal the structural efficiency and impact of any resonance phenomena concerning the water mass between the two structures.