How salty is the float tank?
Buoyancy in the float tank is most commonly recorded as a measurement of specific gravity (a comparison of relative densities). With pure water holding a specific gravity of exactly 1, the ocean comes in at about 1.025. Float tanks usually sit in the 1.27 – 1.3 range, making them up to 12 times more buoyant than ocean water.
Ocean water is about 3% salt.
Float tank water is about 35% salt.
The closest experience to this that most people know of is the Dead Sea, a hypersaline lake in Israel known for its ability to keep people afloat. The specific gravity of the Dead Sea is about 1.16, just half that of a float tank.