Experience with floating for 25 min in a sensory deprivation tank.
Frankly, this was a very underwhelming experience. I'm not exactly sure what I was expecting going into this, but it definitely wasn't that. (To clarify, the presentation and hospitality of the spa was superb, and (mostly) nothing was done wrong on their part.)
With my body thoroughly washed and ear plugs installed, I opened the tank door and was met with a mini-burst of humid air. My foot touched the foot-deep 93 °F water, expecting to feel salt crystals or slush or something, but it felt just like regular water. I sealed the door behind me, engrossing myself in the humidity and pitch-black of the tank.
I laid down and lifted my feet up: I was floating! This epsom salt stuff actually worked! With my ears underwater and face sticking out, I remaining static in the water. Opening my eyes made no difference. As I floated there thinking about a variety of things, I began to notice the one noise present in the tank: my heartbeat. Similar to hearing your heartbeat in the world's quietest room, the combination of pure silence and water enhanced the sound of my heartbeat, quickly making for a not-so-comfortable and incredibly distracting experience.
It quickly went downhill from there. I tried to elevate my head using a provided float, but my ears were still in the water listening to my heartbeat. I weighed my options of staying in for who-knows-how-much-longer or cutting my losses and getting out. I got out.
There wasn't much the spa could have done differently, assuming the water was at the correct temperature. My only other gripe was the limited width of the tank. I found myself hitting the sides every so often, which took away from any trance I or someone else would have gone into. Having a larger, square tank would be helpful for this.