[ELI5] How can sea mammals sleep without suffocating under water?

Question

[ELI5] How can sea mammals sleep without suffocating under water?

In: Biology

Answer 1

Different species have different tactics. Dolphins will only sleep with half their brain for 2 hours a piece, remaining still enough that it is called logging. The awake half literally keeps one eye watching for predators and will surface for breath.

https://www.scientificamerican.com/article/how-do-whales-and-dolphin/