while a dolphin likes to keep one part of its brain and one eye open. Some sea birds are reputed to spend so much time covering large distances, that they've developed the ability to sleep while flying. A sperm whale holds its breath as it naps near the surface, while gangs of meerkats like to sleep together, in pelted heaps. As time wears on, I find it harder to fall asleep especially after a long day at work; I come home but my mind's still racing. I envy bats and possums who can sleep through nearly an entire day, waking only to go hunting; or the walrus who, it's said, can sleep and swim at the same time. But first I would need to learn how to get over my fear of water, though I believe it could be one of the most soothing mediums in which to float. Recently I saw an ad for a float tank in a spa, where you can climb into a pod and lie back nearly weightless in salt water the depth of a foot. Then, someone gently pushes close the lid of the tank so all goes dark and external stimulation fades away. The only thing you'll hear is the distant percussion of your heart and your slow, deep breathing. I'm tempted to sign up and try it. Ideally it's a solitary experience, but personally I like how sea otters have sometimes been found holding hands while sleeping, in order to keep from drifting apart.