Evolving to Marine Mammal

Dolphins, apparently, sleep with only half their brains at a time.*  Same for ducks.  And whales.  They can't afford to completely power down all at once.  Dolphins have to remember to breathe.  Ducks have to watch out for predators.  Whales have to take care of their kids after a long night at work.  Wait, no.  That's me.  People mostly sleep with their entire brains tuned out.  Luckily, after years of practice, I've learned to half-brain it when I have to.  And pray for nap time to come.

A deserted park on a sunny day.  I may have slipped into unconsciousness for a few minutes on the warm sand.

*I learn everything on public radio.