noun
seawater; sea water; saltwater from the sea
Refers specifically to naturally salty water from the sea or ocean. Although it can be translated as “saltwater,” artificially salted water is more often 塩水.
海水を飲むと、かえって喉が渇く。
If you drink seawater, you actually get thirstier.
この魚は海水で育つ。
This fish grows in seawater.