From Longman Dictionary of Contemporary Englishseawatersea‧wa‧ter, sea water /ˈsiːwɔːtə $ -wɒːtər, -wɑː-/ noun [uncountable] salty water from the sea
Examples from the Corpus
seawater• Tubeworms grow so as to keep their plumes in the region where the vent water and seawater mix.• There is plenty of oxygen in the surrounding seawater, though.• At most, the mass of water was only a half a degree Fahrenheit warmer than the surrounding seawater.• Constant exposure to seawater, far from having a healing effect, actually caused boils and other skin infections.• When using warm seawater vapour, the plant can also produce fresh distilled water when it is condensed back into a liquid. 