Zazen's name doesn't tell you what goes on inside the Marina District building.
"You know, we try not to build too many expectations before people go in," floatation instructor Darin Lehman said.
Maybe the sign next to the front door will help -- mediation, massage, yoga and floatation.
"When you step into the tank for the first time, it's a little weird," Lehman said.
Lacy Hickox is heading for the tank. She works at Zazen and is a devoted floatation fan.
"It's warm, salty and buoyant, it's about 95 degrees," she explained.
In the past it's gone under the name sensory deprivation or isolation and now floatation. Its' roots are in neuroscience and it's been used by everyone from top athletes to help with focus to interrogators to help soften up a subject for questioning. But, now the object is stress relief.
Kane Mantyla runs a competing business in San Francisco called Float Matrix.
"I watch people come in old, tired, stressed and they leave like kids," he said.
The concept is pretty simple: you lie in a pool of 75 percent water and 25 percent Epsom salts. The water is heated to near body temperature; the Epsom salts keeps you floating. An elaborate filtration system keeps the water clean. Inside, floating in total darkness and absolute quiet, the subject has nowhere else to go besides his or her own head.
"As the magnesium causes the muscles to release and the body relaxes, the mind kind of blisses out," Mantyla said.
For some people that may mean hallucinations or a piercing look deep inside one's consciousness. It can also be claustrophobic and anxiety-causing for some, but, not for most.
An hour of floatation will cost about $75. Be ready to shower before for cleanliness, and after to get wash away a layer of salt residue. Bathing suits are optional.