This paper describes the development of, and results obtained from, experimental and mathematical models of a novel vapour compression desalination system which utilises the power of ocean waves directly. The results demonstrate the feasibility of this concept and provide preliminary data on which to base a full-scale design, Indications at this stage are that fresh water produced at the 1000 tonne/day scale in favourable wave climates would be substantially cheaper than that obtained from conventional fossil-fuelled plant.