Are there any animals that never sleep?

My cat, who may or may not honestly mistake my prone figure for a trampoline during the night, will never let me see him with his eyes closed. He thinks it’s a sign of weakness that might allow me to permanently assert MY dominance in the house I paid for. But cats aside, it’s the dolphin that comes to mind.

Dolphins can’t go to sleep. They are mammals, need to surface to breathe and will drown if they doze off. And underwater is the only place you won’t find a Starbucks.

Not to worry. For eight hours a day dolphins are fully awake, but the rest of the time they’re on cruise control. In those 16 hours, half of their brain is asleep for one eight-hour stretch, while the other half snoozes during the next eight-hour shift. Moral: to beat a dolphin at chess, first check his schedule.

Source: Do Fish Drink Water? Puzzling and Improbable Questions and Answers by Bill McLain