I assume water to them is analogous to air for us and is the medium they are living and breathing in. But all organisms (to my knowledge) require water to survive and so the idea of them drinking a small amount of the water they swim in every now and then seems ridiculous to me.
In: Biology
Freshwater fish swallow and expel water through their gills through a process called osmosis. They also swallow water when they swallow food, and this water too gets expelled through the gills.
Saltwater fish deliberately swallow water to maintain the salt concentration in their body. If the salt concentration in body goes high, they’ll expel the excess salt and swallow more water if the salt concentration goes down.
No, they could drown.
Some do! It depends on if they’re in fresh water or salty. There’s this thing, osmosis, where water tries to even out the salt concentration so it will go from where there’s less salt to where there’s more. As a result, freshwater fish get enough just by existing (because the salt concentration in their bodies is higher than that of the water they live in) while saltwater fish do need to ingest some water because they live in, well, salty water. And both have ways of maintaining their salt levels do they don’t get too high or low.
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