Seaplanes were an important feature of aviation during its first four decades, both for long range transport and high airspeeds. Research, and the testing of new designs, was carried out at the Marine Aircraft Experimental Establishment at Felixstowe until 1958. However, the record of this scientific work at MAEE has never been fully reported until this paper. The main scientific topics described are, stability during take-off and landing, hydrodynamic resistance, landing impact, spray formation and its control. Armament research and testing receive special attention. A large fleet of prototype seaplanes was type tested; results from these type tests are summarised to show the wide range of designs needing to be assessed. In a final section the authors consider how seaplanes may return to the main stream in the 21st century.The two authors were respectively Head of the Scientific and Technical offices at MAEE in the 1940s.