Over the decades, the flotation fad drifted in and out of consumers’ consciousness. Sensory deprivation got some notoriety from the 1980 sci-fi flick Altered States, but isolation tanks never gained widespread acceptance.

Then flotation got a facelift. Instead of being enclosed, some were designed to be open, with less emphasis on total sensory deprivation and more on relaxation. Flotation therapy spread across Europe, and more than 50 facilities popped up across the United States.

In Colleyville, former Texas Rangers first baseman Pete O’Brien had long been intrigued by flotation as a way to relieve stress and improve well-being. After investigating the psychological and physiological benefits, Pete and Donna O’Brien opened At Peace Floatation Spa this summer.

Pete O’Brien found that floating in a zero-gravity environment left him feeling relaxed and that the anti-inflammatory effects of Epsom salts eased the pain of past sports injuries.

"You come out much more at ease and at peace," he said.

Dr. Jeff Connors, a Colleyville chiropractor, said floating can speed healing and "reset the body’s circuit breaker." He recommends flotation to athletes and does it himself. "To me, I felt like I was walking on clouds," Connors said.

Dr. Scott Stoll, a professor at the University of North Texas Health Science Center, remembers using his father’s isolation tank when he was growing up. Anything that helps people relax is beneficial, he said.

"You can sit at home in your easy chair, you can get a massage, you can learn to meditate or you can lie in one of these isolation chambers," Stoll said.

For Type A personalities who have a tough time unwinding, floating is a way to shut down the brain, Pete O’Brien said. Some people experience a heightened awareness of color, sound and clarity of mind.

Without the distractions of light or sound, the body naturally relaxes, he said.

"When you are in that restful place, you don’t move; you don’t even know you’re in water," Donna O’Brien said. "You lose all concept of time."

Here are the flotation facts:

The environment: Temperature-controlled suites contain a spa about the size of a twin bed with 10 inches of Epsom salt water warmed to body temperature. Spa users must shower before and after use. Many choose to float wearing bathing suits or swim trunks. Buttons in the spa control music and lighting. The user can float in silence or can select from meditation music or guided imagery — a gentle voice from the sound system that guides you through relaxation techniques. There’s an intercom that can be used if needed.

The experience: The salt water is so dense that any body, regardless of size, floats effortlessly. Some people feel as if their body is drifting away into a dreamlike state. It is common to fall asleep. A one-hour session is said to have the restorative effect of four hours of sleep.

The hygiene: The idea of soaking in someone else’s water might turn some people off, but a filtering and sterilization process is used to keep the spa as clean as possible. Epsom salts also kill bacteria.

The benefits: Floating is said to boost immunity, reduce high blood pressure, diminish depression, speed the healing process and promote circulation. It also is said to reduce symptoms associated with asthma, insomnia, fibromyalgia and rheumatoid arthritis. It has been used to improve concentration and creativity.

The proof: Since the 1950s, when sensory deprivation isolation tanks were introduced, more than 100 universities have studied flotation. Numerous athletic teams, including the Dallas Cowboys, have used tanks. Carl Lewis used it to prepare for the 1988 Olympics. At the 2000 Olympics, more than 200 flotation tanks were available for athletes.