Brackish water, seawater.
https://www.emergency-wash.org/water/en/technologies/technology/brackish-water-seawater
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Brackish Water has a higher salinity than freshwater, but it is not as saline as Seawater. It occurs naturally where Seawater (salt water) and fresh water mix, as in estuaries or in brackish fossil aquifers. In an emergency, Brackish Water might be the only available source, and it is possible that it is already in use, or in the case of Seawater, it might already be used as part of a pre-existing desalination plant.