Abstract: A wave-actuated system for desalination of water by reverse osmosis (RO) has at least one offshore wave energy converter subsystem for pumping salt water and supplying the pumped salt water via a water outlet, a pretreatment subsystem hydraulically connected to the water outlet of the at least one offshore wave energy converter subsystem, and a RO desalination subsystem receiving filtered water from the pretreatment subsystem. The at least one wave-energy converter has a float and a hydraulic cylinder pumping salt water to the RO desalination subsystem. A method for operating a reverse-osmosis desalination subsystem using pressurized salt water supplied by at least one wave energy converter subsystem is described. A method for making a hull is also described.