Since this is an article about float spas, I’m obligated to mention the 1980 film Altered States, in which a psychologist decides to mix “floating”—as the practice is sometimes called—with psychotropic drugs in an effort to expand his consciousness. Wild, terrifying shit ensues.

Needless to say, if you’re considering a visit to a float spa, avoid the movie Altered States at all costs.

As the release date of that film suggests, floating and isolation tanks have been around for decades, but they’ve experienced a small resurgence in recent years. The “therapy” involves spending an hour or two in a water-filled chamber. The water is 10 inches deep and pre-heated to roughly 93 degrees, which is the temperature of the surface of your skin. It’s also packed with enough Epsom salt that you’re able to float on top of the water like a carefree ocean buoy.

The isolation chamber is also soundless and lightless. The idea is to deprive your brain and body of all sensory stimulation. There’s evidence the practice helps reduce stress and anxiety, and some research has shown it boosts creativity, concentration, and motor performance.

The evidence on all these benefits is contentious, but not dismissible. Like yoga, meditation, and other forms of holistic therapy, some people say floating has changed their lives.

My visit to Halcyon Floats in Philadelphia began with a thorough run-down of how to prepare my body for the isolation tank. After removing my contact lenses, I entered a private room containing my chamber and a shower. The float tank’s water isn’t changed between guests, so the spa’s owner, Keri Rakickas, instructed me to thoroughly wash my hair and body before entering, which I duly did.

Naked but for earplugs, I climbed into the tank holding a neck pillow Keri said might be helpful if I found it difficult to fully relax my head and shoulders in the water. “Especially if you’re not used to it, there’s a tendency to try to hold your head up,” she’d told me.

Isolation chambers come in various shapes and sizes. My tank—and there’s really no other way to describe it—resembled a giant coffin. As I climbed inside, the water felt warm and pleasantly slick. I tucked the neck pillow into a corner, closed the door, and eased back into the darkness. After a few seconds of bobbing around, the water calmed and I was able to float without drifting into the walls of my tank.

Keri had told me to dry my face well after showering, and I thought I had. But a few missed droplets tucked into the crooks of my nose and eyes immediately made themselves known. Since touching your face almost guarantees you’ll get salt water in your eyes, I spent the first few minutes trying to ignore these little distractions.

When the urge to scratch my face passed, there was a brief period when the darkness and lack of sound—both of which were total—felt threatening. I imagined invisible creatures reaching for me out of the darkness. I also thought of that scene in one of the Kill Bill movies where Uma Thurman is buried alive.

But eventually those thoughts faded and I slipped into a place of happy obliviousness. Occasionally a small muscle in one of my limbs would twitch, reestablishing my body’s presence. Otherwise the lack of physical stimuli was absolute.

I’d read up a bit on meditation before my visit to the float spa, hoping it might help me optimize my time in the tank. I think it did. Staring into the blackness, I took deep breaths. As thoughts came into my head, I did my best to acknowledge them and let them slip away. I soon realized I could hear my heartbeat pulsing in each of my breaths. I focused on that heartbeat, and the world receded.

I know there were times when I dozed, though the lack of light and sound blurred the lines between wake and sleep. When music started playing to alert me my 90-minute session had ended, I felt pleasantly disoriented. I wouldn’t say the time passed either quickly or slowly; it was more like I’d lost that connection to time that modern life hardwires us.

Before visiting Halcyon Floats, I’d avoided articles or reviews on float spas. I didn’t want my head filled with expectations or preconceptions based on other people’s experiences. But afterward I read a lot of first-hand accounts. Some minor visual and auditory hallucinations seem common, though I didn’t notice any of those. A fair number of people said they were really put off by the whole thing.

I felt just the opposite. In an age when we’re all continuously bombarded by stimuli—especially the digital kind—I found it relaxing to sink away from all that for an hour and half. I also think it helped that I visited the spa on a Sunday afternoon, when work and other stressors were already back-burnered in my brain.

Was it so enjoyable that I’d go back again? Not sure. Apart from the price tag—a single visit costs between $50 and $80 at most spas—the time commitment was steep.

Then again, stress is a killer. If I wasn’t sleeping, or if I felt anxiety was really starting to mess with my life, I think floating—like yoga or meditation—could be a worthwhile form of therapy.