Taking a dip in very cold water for several hours a week is good for our health. Researchers in the U.K. looked into the benefits of cold-water immersion therapy. They found it could benefit our cognition, sleep quality, and well-being. The researchers studied 13 test participants, who were dunked in 10ºC water for 10 minutes, three times a week, for four weeks. The lead researcher said the cold-water therapy could "help with a number of positive physiological and psychological changes linked to improvements in overall general health and well-being".

Cold-water immersion is used in many fields for its healing benefits. For decades, ice baths have helped to speed the recovery of athletes following energy-sapping performances. The researcher said: "Two weeks of regular therapeutic cold-water immersion improved subjective sleep, with fewer sleep disturbances." Taking cold-water baths for health purposes is already a common practice. At the New Year, people worldwide swim in icy seas and lakes. In Japan, bathers refresh their bodies by dipping in and out of hot and cold baths. This a tradition called toto-no-u.