[Retric]

That’s not quite correct, “some marine mammals are known to drink seawater at least on occasion” https://www.scientificamerican.com/article/how-can-sea-mamma...

They do supplement that with water extracted from their food. But unlike humans they are better at expelling salt. “In the seal and sea lion species, for which measurements exist, the animals' urine contains up to two and a half times more salt than seawater does and seven or eight times more salt than their blood.” Human urine on the other hand contains less salt than sea water resulting in dehydration when drinking sea water.