Stepping inside a sensory deprivation tank is a little strange at first. It's pitch black and the tank itself is soundproof. There's around 850 pounds of Epson salt dissolved in the water so that your body is very much buoyant while you float, allowing your muscles to relax (and if you have a scratch on your body you aren't aware of, you'll know immediately since you're essentially salting the wound!). It smells like salt obviously, but you get used to the smell quickly. The water itself is kept at average skin temperature (~93.5 F), which allows you to lose track of your body.
I've found that floating in a sensory deprivation tank can be similar to that of other forms of meditation in that you're focusing on breathing and watching thoughts arise (though this entirely depends on your own practice). It's also very different simply because you're naked and all the things I've mentioned above - you're not in a constant state of analyzing your sensations and the world. A typical float lasts about 90 minutes which is more than 4x longer than my own average meditation session. Granted, floating is much more comfortable position for meditation than sitting in the same position for an extended period of time, which translates to being more enjoyable. To be honest, the only benefits over traditional sitting meditation is that information from your five traditional senses are dialed way back and your session is much longer.
I've experimented with sensory deprivation tanks around eight or so times and have had a couple interesting sessions - both subtle realizations regarding consciousness and experiences that have resulted in long term lifestyle changes.
I once tried floating while I had a hang over back in 2017. Whenever I had to deal with a hang over I would typically drown out those awful sensations and feelings of self loathing with television, video games, and eating a lot of junk food. Note that this was a regular (at least weekly) pattern of behavior. However, stepping into a sensory deprivation tank instead of doing those things, I faced those raw feelings and sensations head on. I had observed those thoughts of self-loathing that I historically was only partially noticing. After that experience, I swore off alcohol and haven't been drunk since.
On a separate occasion, I had noticed that a 90 minute session went by rather quickly, as though my perception of time were distorted. Thinking back on it, I simply fell asleep midway through and exited the tank feeling refreshed as I had just taken a short nap. Either way, a personal insight here is that that being awake and being unconscious isn't necessarily a hard line between these two states. There are varying levels of wakefulness as there are varying levels to unconsciousness (think of the various stages of the sleep cycle).
Like traditional meditation, sensory deprivation isn't likely going to be a psychedelic experience, though I think it can offer insight into the nature of consciousness at the very least. At most, it can be a catalyst to a lifestyle change.
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