A big technological gap exists between existing surface effect ship (SES) technology and the expected requests from fast ships market in the short-term. The HYDROSES project, led to a substantial improvement in the SES aero/hydrodynamics know-how and to the definition of a design methodology for large fast SES. This was made possible through the integrated and well co-ordinated development and application of advanced theoretical and experimental methodologies. The physical/mathematical modelling of SES aero-hydrodynamics was formulated and theoretical tools for powering, seakeeping and manoeuvering predictions were provided. Existing techniques for SES model testing were assessed and improved and know-how was gained in the proper planning and execution of the experiments. An extensive sea-trials campaign on a purposely hired existing SES was carried out. Finally the target vessel was identified and designed at a preliminary stage and a design strategy for the combined use of software tools, model-testing and sea-trials was outlined providing also general recommendations and guidelines based on the lessons learned in the course of the project work.