We know that spending an hour in a tank of water might sound at first like a David Blaine-style stunt - but in fact this experience is about total relaxation. You'll lie in a quiet, darkened room in a warm solution of Epsom salts, about 10 inches deep and so dense that you'll float effortlessly (no need to be able to swim!). Epsom salts are made from naturally occurring minerals and have long been renowned for their health and beauty benefits, including easing stress and soothing muscles. Gentle music will play to help you wind down, and you'll drift into a near-meditative state of complete calm. Afterwards you can take a refreshing shower before returning to the outside world feeling utterly chilled out.