As far as I know all life needs water to survive. Doesn’t matter if it is a cactus in a desert or a tree in a rain forest, it needs H2O.
What about fish though? They’re surrounded by the stuff, absolutely gallons of it.
Fish are life forms of course and so they too need water.
The type of water that surrounds them plays an important role in how the fish obtain the stuff. The water can be fresh or salt.
Fresh water fish absorb water through their skin. They also have methods of ridding themselves of excess water without losing the important salt within their bodies.
Marine fish are the same in that they need to keep a certain concentration of salt in their bodies. Of course, marine fish are surrounded by salt and water. What they do is drink the seawater and the gills process the water removing the salt. In marine fish it is the retention of water that is the problem, and to combat this some of them have inefficient kidneys or do not have kidneys at all.
Anyone wants to read a bit more here’s a link: