Life on Earth began in water and evolved from it. You have personal experience with this dependence each time you seek water fluids to quench your thirst and replenish your body's water content. The cells inside your body are surrounded by a fluid that is mostly water and your cells themselves range from 70% to 80% in water content. Water is the biological medium here on Earth and the supporter of all life forms.
Water circulates through our body without rest and causes the macromolecules (proteins, enzymes, and genes) and cells in the body to function properly. When information is passed from tissues to tissue, it is water that delivers this information. Water performs not one but many particular tasks, all life supporting or life saving. In a living body, if the circulation of water slows down too much, life ceases. Equally important to both lower and higher organisms, water is the vital generator of life and its supporting force.