Floating enables your brain to produce low frequency Theta waves. Theta waves are normally only present as we drift off to sleep or right before fully waking.
During wakefulness and normal levels of alertness, high frequency Beta waves are present. Beta waves are also associated with patterns of “overthinking.”
Floating removes the external stimuli that keeps the brain constantly moving, thereby replacing the beta waves with theta waves. This “theta state” helps our brain achieve an unusually deep state of relaxation.