I bought it as an expensive, therapeutically perfect gift for a stressed-out friend with back, foot, teeth, and job pain. What better present to give her than one hour of being held, with no obligations or responsibilities to the holder (which, in this case, is 10 inches of skin-temperature water with so much Epsom salts—1,000 pounds—that you are weightless and buoyant)?

In 1954, sensory deprivation tanks of such a concoction were invented by neuropsychiatrist John C. Lilly to further his understanding of the brain’s energy source. In the last few decades, “float tanks” have proliferated: There are currently 152 commercial centers with tanks in the U.S. listed on this site. I first floated in the late ’80s, after I heard about one of the first commercial centers. The tank was actually a big tub in a chamber within a private bathroom chamber. Relaxation music was optional, pumped in from somewhere under the gelatinous water, and I opted for it. The relaxation was so profound that I lost all relationship to time and was stunned to learn that the tank monitor had given me the gift of an hour and a half, even though I’d paid for only an hour.

Plenty of science—most recently, Swedish researchers at the Human Performance Laboratory at Karlstad University Sven-Åke Bood—has found that repeated float sessions can relieve anxiety, stress, depression, and physical pain. But this probably wasn’t the best choice of a birthday gift for a friend with an undisclosed case of claustrophobia. After a quick visit, she graciously returned the gift certificate to me, which is why I find myself heading to the yoga studio to make use of it.

What struck my friend as a possibly dangerous situation—entering an enclosed box in an unknown venue run by unknown people—looks to me like a return to prebirth. To my eye, the tank in the “float room” is an enormous fiberglass womb, and the concierge is a mysterious mother kind enough to welcome me into a safe home. I can’t wait to get in and release all responsibilities—such as holding up my own sometimes-heavy monkey-mind head.

In The Book of Floating: Exploring the Private Sea (Quill, 1984; a free PDF is available here), researcher Michael Hutchison describes first learning about floating, as many people did, through the 1980 movie Altered States. In a weird twist, I was actually in the original cast of that movie, when it was slated to be directed by Arthur Penn. It wound up being adapted by Paddy Chayefsky from his own novel. In the opening to that book, Chayefsky describes the 1965 version of what I’m about to do: “The isolation tank itself is nothing more than a coffinlike bathtub . . . eight by eight by ten feet and half filled with a 10 percent solution of magnesium sulfate in water to increase buoyancy. The water was heated to 93˚F, the temperature at which a floating body feels minimal gravity….Inside the tank, the volunteer subject floated in utter silence, effectively deprived of sensory stimulation, alone, isolated.”

The air in the float room seems hot—81˚F, according to the thermostat—but the people who run it must know what they’re doing. I remove my robe, take a couple of photos of the pod, and put in earplugs, as required. I doubt that I’ll morph into another creature as I discover the origins of human consciousness the way Chayefsky’s protagonist does, but I step into the big white pod not knowing what will happen. Will I have insights? Will I lose time the way I did in my float almost 30 years ago? Will I stop obsessing about work? Will I re-experience being in my mother’s womb “or even beyond that to the first cell of [my] conception,” as Chayefsky writes? Or will I just have nicer skin—one of the well-documented benefits of full-body magnesium absorption?

In a recent in-depth Discover article, “Floating Away: The Science of Sense Deprivation Theory,” journalist Shelly Fan says that more than 90% of subjects find the floating experience “deeply relaxing,” so at the very least maybe I’ll take a badly needed nap.

After less than 30 seconds of breathing a cloud of H₂O-saturated air, I have new empathy for my claustrophobic friend—and for waterboard victims. The two little vents in the top of the tank simply do not supply enough O and I decide to float with the pod door ajar.

Ah. Peace. Almost immediately, my only thoughts are of my body. From the collarbone down, I’m in heaven, but my chronic tension areas—my neck and occipital lobe (lower back of my skull)—are in pain. It seems that even in water, my habitual holding in those areas won’t let go. I cradle my head in my hands—whoa! you can’t do this in regular water without sinking—and find instant relief. I could do this forever. But what if my time runs out too soon? Oh, no, I’m thinking too much. Hey, what’s that music?

Am I having an auditory hallucination? Chayefsky and many others wrote about such things. Over and over, droning chords. I’ve read about a spiritual experience of heavenly music, but this stuff is annoying. Why am I hallucinating annoying music…and the distinct sound of bodies thumping? And voices?

Apparently, the pod is not soundproof when the door is open. But if it’s a choice between suffocating and tolerating annoying sound, it’s no contest.

Okay. So I’m not going to have the silence I longed for. Will I spend my hour obsessing about that, or will I accept the situation and see what else might happen? To be honest, I’m ambivalent. The sound seems to shoot up through the water. I breathe. Boy, my breathing is loud. I experiment with flapping and bounce from one side of the tank to the other—fun. I touch my eyes—bad move; I was warned that the water would sting. And finally I do absolutely nothing. Nothing. Nothing. Annoying sound. Nothing. And suddenly—

“Five minutes,” calls an attendant, cracking open the float room door.

“That’s fine,” I answer groggily, squinting at the assault of the light. “By the way, is there music playing?”

“Oh,” she says, “that must be the Spanish dance teacher. He started class a while ago.”

“Ah,” I answer.

Am I annoyed? Yes. Am I physically relaxed? Yes. Is my skin gorgeous? Unbelievably! Like silk. Would I go back? Not to a tank in a yoga/dance studio. So here’s my advice:

• If you’re claustrophobic, stay away from pods; find a center with a big tub instead.
• Ask whether the tank is soundproof even with the pod door open.
• Then commune with your Self like there’s no tomorrow!

Read about Betsy Robinson.