The aim of PSP project (Partially Submerged Propellers project) is to develop a new technology for the design and the manufacturing of highly efficient and innovative ship propulsion system. The intended propulsion system is mainly characterized by large and particular propeller, purposely designed to operate partly submerged for some or all the expectable loading condition of the vessel. Ships provided with PSP may also be distinguished by a peculiar design and arrangement of stern forms, rudder, tailshaft, reduction year box and main engine.Energy savings connected with the application of the PSP concept are expected to be remarkable (in some cases more than the 30%). The relevant economic, industrial, social and environmental effects are therefore expected to be extremely interesting. In view of the extreme degree of innovation, difficulties and risk involved, it is considered that the intended research project and the development on vast scale of the proposed new propulsion system will require comprehensive investigations to be supported by suitable experimental tests both with models and in full scale.