Actually not a lot of animals do that, but yeah, dolphins are the best example. When they sleep, half of their brain shuts doen, so they operate with one half of their brain and only one eye works. Its pretty cool! Now that I think about it, I am not sure of any other animals do that, if so could you remind me. I wish we humans could do that, but i figured only doplhins could becasue their brain is move developed then ours.