Have you heard of floating? No, this isn’t a relaxing float in the pool — it’s a certified spa treatment.

In “float therapy,” guests lay in an enclosed water tank (also known as a pod) filled with enough Epsom salt to keep a body afloat without tensing any muscles. The sensory deprivation of floating is meditative and comes with a slew of benefits, such as stress reduction, pain relief and improved blood circulation. It can even help relieve PTSD symptoms in military veterans.

The concept of floating as a therapeutic experience was invented in the 1950s by neuroscientist John C. Lilly, who wasn’t taken seriously by the scientific community. In the 1970s, Thomas H. Fine attempted more research, but funding was rejected because floating was seen as “a hippie fad.” The 1980 movie “Altered States” didn’t help; the film was inspired by Lilly’s research and depicts a scientist who experiments with floating and goes mad.

This hasn’t stopped the scientific community from researching the potential benefits of floating. A study authored by Fine in the 1990s, for example, revealed floating was associated with decreased levels of cortisol, a stress hormone. A study in the International Journal of Stress Management in 2006 revealed that multiple float sessions reduced pain, stress, anxiety and depression for a study group of 70 people, with the effects continuing up to four months after float treatments. Currently, neuropsychologist Justin Feinstein, based in Tulsa, Okla., is scanning the brains of healthy people with an MRI before and after a float session. Next year, he plans to run the same experiment on people with PTSD as part of the same study.

Today, floating is readily accessible — there are more than 250 float centers in the U.S. A 60-minute session will cost anywhere between $50-$100.

Kathryn Howard is Assistant Editor of AQUA Magazine.