We are all so highly stimulated these days, it's hard to find any free time and just sit and be alone with your thoughts. Floating allows us to switch off from all our day to day problems, and like meditation offers us the chance to just be in the moment.
With the lack of a sensory input we are able to relax to a point where we reach our theta state (Usually achieved before and after waking). This is associated with creativity, problem solving and advanced learning.
Also with the natural curvature of the spine in the floating position floating is also a form of spinal decompression and has been reported to reduce blood pressure and increase blood flow.
Other floaters also credit the reduction of certain issues including stress, anxiety, pain, swelling, insomnia and jet lag to regular sessions.