Floating is a relaxation and therapeutic technique that involves restricting sensory input to achieve a deepened meditative state. You get in a floatation tank filled with 10 inches of a high concentration Epsom salt, water solution. The density that results from 800lbs of epsoms salt makes you completely buoyant and so you just lay down and float. The water is the same temperature as your body so you don't feel anything.
There is no light, no sound, just you alone in the still calm.
Soon you are so relaxed, you can't tell where you end and the water begins — you feel like you are levitating. This triggers the release of endorphins, your muscles and spine loosen (almost zero gravity!) and you just experience extreme peace and clarity of thought. It's just you, exploring and experiencing your own mind, while the salt soothes and detoxifies your body.