The popularity of high-speed craft is steadily increasing. Until now, much attention has been focussed on the hydrodynamic aspects of these craft. The structural design of these vessels is usually considered in a quasi static sense. However, due to the requirement of light ship structures, fast ship tend to be flexible. This flexibility combined with high service speeds and high propulsion thrusts, causes a dynamic response to occur rather than a static. Moreover due to high speeds and high propulsion powers, the probability of impact by waves (slamming and wave slap) increases significantly. Therefore the consequences in terms of both global and local huil damage become more serious.