A desalination system that is deployable in a body of water having a surface and a seafloor and which includes a vessel structure that is capable of travel in water, a reverse osmosis system disposed within an internal space of the vessel structure and a tank connected to the reverse osmosis system, the tank configured to receive filtered water from the reverse osmosis system. A positioning system is provided for controlling the travel of the vessel structure, and a ballast system is configured to control the buoyancy of the vessel structure. A controller is operably associated with the positioning system and the ballast system to control the position of the vessel below the surface of the body of water.