David Cain spends 90 minutes in a darkened sensory deprivation tank:

With no stimulus, time really seems to stretch out. After I’d lost track of my body, I realized I had absolutely no idea how long I’d been in there, only that it could only have been a fraction of the full 90 minutes. By that time I was extremely comfortable, much more comfortable than I ever get in bed or in an armchair.

One completely unexpected effect was that my ability to imagine became supercharged. I pictured being in a hammock on the beach, and some very specific details came flooding in — the smell of hot sand, the feel of my bare feet on a sunlit nylon rope, the sense of being away from Canada, even.

That must have been quite an experience. Although looking at those tanks, I wouldn’t get in there in a million years if not for the fact that there’s no lock on the door.