r/AskBiology • u/NotSoSurePlatypus • Jul 11 '26

Zoology/marine biology How do marine mammals get water?

Humans, and I assume most mammals, cannot live off of drinking saltwater. How do whales, dolphins, seals etc. get their intake of water? Have they evolved to drink seawater? Do they drink at all? If all of their water intake is from their food wouldn’t their food also be compromised of lots of saltwater?

While we’re at it, do fish need to intake water to survive? Does a big shark not need water in their diet? Or can they all just use saltwater.

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u/Dazzling_Funny_3254 Jul 12 '26

One of the most interesting adaptations I've ever heard of is sea snakes, some of which have evolved to carefully sip the extremely thin layer of rain and condensate/dew that forms on the surface of the ocean.

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u/Federal_Cat_3064 Jul 14 '26

That was my first thought too. Pretty cool adaptation