Methods and systems are disclosed for desalinating saltwater. The method includes (a) drawing feed water from a body of saltwater at a given depth below the surface of the body of saltwater; (b) transporting the feed water to one or more reverse osmosis vessels submerged in the body of saltwater and located a depth greater than the given depth at which the feed water is drawn in step (a); (c) controllably desalinating the feed water in the one or more reverse osmosis vessels to produce freshwater and brine concentrate such that the salinity of the brine concentrate is substantially the same as the salinity of the saltwater in the body of saltwater at a predetermined depth below the surface of the body of saltwater; and (d) discharging the brine concentrate into the body of saltwater at the predetermined depth below the surface of the body of saltwater.
