Humans are known as involuntary breathers, while dolphins
are classified as voluntary breathers. Humans do not
have to think about breathing, they just do it. Dolphins
on the other hand, have to think about every breath
that they take.
Now you might be wondering how dolphins are able to
rest, and continue to breathe. Dolphins sleep with only
half of their brain at a time. They sleep with one eye
open to look for predators while also staying alert
enough to take a breath when required. In this way,
the animal is never completely unconscious, but they
are still able to get the rest that they need.