Fish get thirsty too! So how do they drink water?

Fish actually take water into their bodies by absorbing it rather than drinking it.

This occurs through a process called osmosis as water attempts to reach equilibrium.

HOW IS THE NEED FOR WATER DETERMINED?

Whether fish need to drink water depends on how much water is gained or lost from their bodies during osmosis—the process of filtering and absorbing water based on the concentration of salt in the water versus the salt in their bodies—as well as whether they live in fresh or saltwater.

In freshwater fish, body fluids are much saltier than the water surrounding them, and therefore, in search of chemical balance, fish absorb water through their skin and gills via osmosis.

NOT EVERY FISH IS THE SAME!

As a result, freshwater fish generally do not need to "drink" much water; if they were to drink too much, the salt concentration in their bodies would become so low that their muscles and nervous systems would not function properly.

That is why these types of fish urinate almost constantly to expel excess water.

On the other hand, saltwater fish need to do this to keep everything in balance.

Water constantly flows from their less salty internal organs through their skin and gills into the surrounding, saltier water, so fish direct some of the water they take into their mouths to their digestive systems rather than their gills.

However, there is a problem here.

Even though water is highly needed, if saltwater intake is not controlled, there is a risk of having too much salt in the body, which is just as problematic as having too little.

To prevent this, saltwater fish have special cells in their gills that pump salt out.