People have found that it can take as little as 15 minutes in the float tank to induce a meditative state equivalent to that of a skilled mediator with many years experience in meditation technique.
Many people find it difficult to find their complete center while meditating. This can take years of practice. It has been shown that you can reach that calmed inner peace in as little as one session. This depends on how open you allow yourself to become.
For relaxation, one simply floats and 'clears the mind.' Floating has many different techniques. One may perform meditation, mantras, self-hypnosis, utilize educational programs, etc. The idea of floating is that, when the body is relaxed, the mind becomes highly suggestible and any action taken during these states will enter the information into the sub-conscious.