A simulation method is presented to improve small craft harbor design by studying the behavior of moored vessels in small craft harbors, using physical modeling in medium size wave basins. Two consecutive models of different scale are used in a medium size basin. Transfer functions of vessel movements and mooring and fender forces are determined in the first model, for representative types of vessels moored alternately at a solitary berth, under simulated inside harbor conditions and for various sea states and directions. Near berth wave spectra are obtained in the second model for sea states covering the local climate. Integration of the wave spectra with the transfer functions leads to response spectra of vessel movements and forces. Maximum movements and forces are determined from the response spectra and are used together with limiting criteria and the long term wave statistics to choose the optimum configuration of: harbor layout, types of berth structures and mooring and fendering systems.