In college, I became a NAUI certified scuba diver. We were getting our certification in the fall, at a 200ft deep rock quarry that had hit the water table and filled with 54 degree F water. After a day of diving there, despite the heavy wetsuit I was cold as a mother. I'd rented 3 tanks, and there was still about a half a tank left after the day's diving - which gave me my idea.
I'd recently seen the film Altered States, the source of my inspiration. I would convert my bathtub into a sensory deprivation chamber. I ran a good hot bath in the oversize 1920's tub our apartment had. I ran two strips of duct tape over my dive mask so that the blackout would be complete. I poured some tablesalt into the bath, then strapped on my weightbelt so I'd sink to the bottom. I knew that I was technically supposed to float, but I didn't really see that working. I set the tank next to the tub and put on my mask. I killed the lights, stuck the regulator in my mouth and climbed in.
I don't know how much it was a sensory deprivation chamber so much as an artificial womb big enough for a 6'2" grown man. Whatever it was, it was fantastic. All there was was warm water and the sound of my own breathing. My limbs unknotted, floating into "neutral posture." Time passed.
Then one of my roommates came home from a night of drinking, to be confronted by the sight of a pale insensate body floating in the tub with the lights out. First there was screaming, causing me to shoot up out of the tub, blindly thrashing about in my blacked-out mask. I fell over, skidding naked across the floor as my drunken roommate recoiled from the bathroom in horror.
Couldn't recommend it enough - just warn your cohabitants.