It really seems strange that fish drink water but it’s true. However, all fish don’t drink and which drink, not because of being thirsty but to maintain their body concentration. Actually, the principle of osmosis is the basis of such activity.
Freshwater fish have high salt concentration in their bodies as per the osmosis movement of liquid taking place from lower to higher concentration. Fish have to excrete water up to ten times of their body weight. Whereas in case of saltwater fish, their surrounding water is of very high salt concentration, so they actually drink a huge quantity of water; otherwise, they can be hydrated. Freshwater fish only imbibe water so that they may respire by drawing oxygen from it and release such through their gills. They also urinate in a large quantity so that their body tissues may be prevented from being watery.
