Ever wondered how dolphins, whales, and seals sleep if they require frequent surfacing to breath? Dolphins are known to sleep and stay conscious simultaneously as they lack autonomic breathing. They sleep close to the surface of the water, either by maintaining a steady swim pattern or just floating.

And during their sleep, they keep one eye open. In other words, only one hemisphere is at deep sleep while the other in a state of wakefulness. This keeps them 🐬 aware of their surroundings, alerts the time to surface for air, and maintains other conscious functions. This is known as unihemispheric slow-wave sleep. Fascinating!