Is there any real science behind the urban float craze?

By Jane Hu
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A sensory deprivation pod at Fremont's Urban Float. Photo: Urban Float

By Jane Hu

You’re going to die in here, I thought to myself. I had never felt claustrophobic before I lay down in this coffin-sized tank of warm, salty water, but I felt a panic attack coming on. My rational brain knew I was safe – I was just floating in a sensory deprivation tank, and could leave its dark, stuffy confines whenever I wanted – but it felt so wrong to be feeling nothing.

Floating tanks are designed to eliminate sensory input. The tanks block outside noise – and floaters are instructed to wear earplugs to minimize the sound of water sloshing around them. They are completely dark, save a faint blue light that floaters can choose to flip on, via a button on the side of the tank. The water is extremely salty, effortlessly supporting the floater’s weight, and is heated to skin temperature, so it’s hard to tell where you end and the water begins.

The technique was established in the ‘50s by John C. Lilly, who studied sensory deprivation at the National Institutes of Mental Health. (Lilly left the NIMH after determining the government agency stifled his creativity; he later undertook a project teaching dolphins to speak, and was convinced that the universe was governed by a council of cosmic beings.)

“Relaxation tanks” were big in the ‘80s, but their popularity lost steam in light of the AIDS scare. The last few years have seen a resurgence in their popularity. Since 2012, there’s been an annual Float Conference (in Portland, of course), and small float businesses have cropped up in major cities across the world. There are two in Seattle: Float Seattle in Greenlake, and Urban Float in Fremont.

It’s no wonder that the concept has been embraced by urban dwellers. From rumbling trucks, smartphone screens, and crowded sidewalks, city living accosts the senses. Floating offers a refuge from noise and clutter. Float businesses advertise the health benefits of sensory deprivation, claiming that it improves creativity and mental clarity while eliminating stress. Some offer science-y explanations to back up these claims, citing studies about adrenaline, cortisol and dopamine. But are these claims scientific, or just advertising? I had to try floating to believe it.

By the time my Tuesday evening float appointment rolled around, I was ready for some peace and quiet. I had spent the day elbowing my way through Pike Place Market, texting with friends to make plans and riding jerky buses, but the chaos dissipated as I walked into Float Seattle.

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The lobby at Greenlake's Float Seattle. Credit: Float Seattle

My float chaperone spoke in the softest zen voice, and reassured me that my earliness was not a problem – and he offered to extend my hour-long float by half an hour. He showed me to a private room where I was to strip down, shower, insert earplugs, turn off the lights, and climb into the tank.

After I closed the tank door behind me, I bobbed in the water, left alone with my thoughts. I generally think of myself as a fairly relaxed person, but floating took me to all the worst corners of my mind.

Is it possible to suffocate in this tank? Why did I agree to this? What am I supposed to do for an hour and a half? I could be doing real things, like packing for my upcoming trip or going to the gym. And what is this salt water doing to my hair? Has it been 20 minutes yet? 30 minutes? I feel nauseated — what if I puke in this tank?

This worst-case-scenario thinking went on for awhile. There’s no way to tell how far into the float I finally calmed down, but I was a lot happier after I accepted the loss of my senses. I closed my eyes, concentrated on my breathing and let the salt water carry the weight of my body. I drifted into a trance, but couldn’t actually fall asleep.

Float tank enthusiasts might say that this trance was my experience of increased theta waves, which occurs in sensory deprivation, meditation and sleep. There’s some experimental evidence that the relaxation that comes from floating has therapeutic purposes; a meta-analysis of 27 studies on floating (also called Restricted Environment Stimulation Therapy, or REST) found that it’s associated with lower cortisol and blood pressure, improved people’s sense of well-being, and even improved jazz musicians’ and basketball players’ performances days later.

Another study found that it decreased people’s self-reported levels of anxiety, and and it has been used to treat pain, chronic whiplash-associated disorders, PTSD and depression. REST is seen as an alternative to other unconventional treatments like hallucinogens, because it appears to produce some of the same positive outcomes, but with fewer side-effects, like anxiety. After all, you can leave a float tank whenever you want, but you can’t leave a drug trip.

When I heard the soft music that signaled the end of my float, I felt both disappointment and relief. As I climbed out of the tank, the cool air and lights were a shock — I had to sit down in the shower as I washed off the salty water. As I dressed, my winter clothes felt strangely heavy on my body.

“Welcome back,” my float chaperone said as I exited the room, and he handed me some bottled water. “Be sure to rehydrate after all the salt. You’re welcome to stay here as long as you like.” As I struggled to re-acclimate to the bright, loud world outside the tank, I made small talk with a man waiting for his appointment. He was a long-time floater; he’d estimated he’d floated over 50 times.

“I’m kind of addicted,” he said. When I finally left the Float Seattle building, I felt tingly, warm, and very loose — a whole-body high that lasted for hours.

I felt great after my float, and I wondered what exactly was happening in my body to make me feel that way. Did the lack of sensory input relax me, or just the act of setting aside an hour and a half to do nothing? Was it an influx of endorphins, as float businesses’ promo materials suggest?

It turns out that science is not yet sure why REST works. The claims float businesses make about increased endorphins and decreased stress hormones are reasonable guesses, but there exists little scientific evidence to support those theories. The data behind REST studies are typically people’s self-reports of their experiences, or physical measures after floating. That data tells us how people feel and the state of their bodies after floating, but it can’t tell us what’s happening in their brains and bodies while floating.

For all we know, these positive effects could be a placebo effect — people expect to feel better, so they do – or could be achieved through simpler means, like traditional meditation. We may never know for sure – it’s actually impossible to obtain an accurate objective measure of brain waves or hormones since electrodes and monitors would fundamentally change the float experience.

Back out in the lobby, I noticed a beautiful leather-bound book on the bench beside me. It was full of contributions from past visitors: doodles, words of inspiration, accounts of first floats and epiphanies from the tank (my favorite: “YOU ARE INFINITE”).

Scientific effects aside, it was obvious that floating has helped plenty of locals feel better about their lives, if only for a few hours. And that counts for something.


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About the Authors & Contributors

Jane C. Hu

Jane C. Hu

Jane C. Hu is a freelance science writer. Her work has appeared in Slate, Nautilus and Pacific Standard. You can find her at, or on Twitter as @jane_c_hu.