Dolphins are special animals. They can breath under water and over water. They have a mind that works differently than us. When we sleep, we close both our eyes, and our mind “shuts down” as we could say. But for them, when they close their eyes to sleep, one part of their mind “shuts down” while the other one is still working. They use this method so that they could still see if a predator is close to them and also, so they don’t forget to breath once in a while!