It’s not a no-brainer--it’s just a half-brainer.
This is Sandra Tsing Loh with the Loh Down on Science.
Dolphins engage in unihemispheric sleep: that's the ability of half of the brain to snooze while the other half stays wide awake and active.
Why sleep only halfway? If dolphins slept like most animals, shutting down all activity, they could drown or get eaten. So says Brian Branstetter from the National Marine Mammal Foundation.
How efficient is this neat trick? To find out, Branstetter and colleagues put two dolphins into a floating pen and tested their ability to use echolocation to find underwater objects. Over two weeks the dolphins performed their mapping tasks almost perfectly, without a break, and with no signs of fatigue.
Clearly they can take care of themselves with one side of their brain, while the other half gets forty--or maybe just twenty--winks.
Truth is, most college students have been using that half awake/half asleep brain thing for years. Maybe not so academically impressive but at least they don't get eaten. Much.