system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When out of the water, why do whales and dolphins need to be kept wet? Aren't they mammals who breathe oxygen?
gpt
Their skin does not have UV protections or protective oils so they dry out quickly. 

Their body heat regulatory systems are designed to dump heat into water, so they overheat when only able to dump heat in the much less dense air. 

And most die from their organs being crushed by their own weight since they are designed for water to support much of their weight.