system
Given the following post, respond as if you're commenting on Reddit:
human
What do aquatic mammals drink?

Mammals need to ingest fresh water to survive, right?  Seals, whales, etc. are mammals that live in salt water.  So how do they stay hydrated?
gpt
Please note that they don't perspire, and have a much lower need for hydration.

The little they need, however, they extract from their food, and they use their specialised kidneys to regulate their salt levels in case it is too high, but they **don't** drink salt-water.