How do dolfins sleep without drowning?

Question

Dolfin's breathe air (since they are mamals), so how do they sleep in the ocean?

Answer 1

Dolphins have very different brains compared to humans. Most sleeping mammals go through a stage called REM sleep, which hasn't been observed for dolphins. However, some experiments have shown that sleep-like brainwaves tend to occur within dolphins separately for each brain hemisphere (brain hemispheres being the the two halves of the brain). So, this means that dolphins sleep one hemisphere at a time, allowing for them to control their voluntary respiratory system and watch out for predators.

Answer 2

Dolphins are able to sleep one brain hemisphere at a time so that they don't drown. The hemispheres of a dolphin are much larger than humans and look almost like ram horns. When the dolphin is tired, it sleeps one side of its brain while that other remains functional for life.

Answer 3

Dolphins don't sleep the way we do. Human sleep means inactivity. But dolphins sleep while they are still active. They only shut down on half of their brains at a time, whereas we humans shut down our whole brain at one time. So they can go up for air while still sleeping.