For the design of fenders and dolphins it is essential to have available an adequate method to describe the berthing maneuver of a large tanker to a jetty. Such a method should result in a prediction of maximum deflection of and maximum load in the dolphins, departing from a certain dolphin elasticity and lateral speed of approach of the tanker. The calculation method generally used up till now is based on the assumption that the kinetic energy of the tanker when it touches the fenders has to be absorbed by the fenders. In fact this approach is based on an equation of motion with a constant added mass coefficient and zero damping. The choice of the added mass coefficient has always been a problem due to a lack of data, especially where the added mass in shallow water is concerned.