Survival skills
A human being can survive an average of three to five days without the intake of water. The issues presented by the need for water dictate that unnecessary water loss by perspiration be avoided in survival situations. The need for water increases with exercise.
Elixir of life
In the eight-century "Man'yōshū", 'waters of rejuvenation' (, ) are said to be in the possession of the moon god Tsukuyomi. Similarities have been noted with a folktale from the Ryukyu Islands, in which the moon god decides to give man the water of life (), and serpents the water of death (sïnimizï). However, the person entrusted with carrying the pails down to Earth gets tired and takes a break, and a serpent bathes in the water of life, rendering it unusable. This is said to be why serpents can rejuvenate themselves each year by shedding their skin while men are doomed to die.