Water is literally the stuff of life for living beings. All life began as single-celled organisms floating in water. In their earliest and simplest form, living things are organized bags of water capable of reproduction, whose “inside” water is held together by a permeable or semi-permeable membrane (“sack” or “skin”) through which nutrients borne by the “outside” water (the environment) pass in, and through which waste passes out.
The simplest organisms live like that today. Bags of water, floating in water, taking what they need from water, passing what they don’t need back to water.
What one organism doesn’t need, another does. Water is the soup, each life takes from other lives via the medium. Without water the planet is barren, a Moon, a Pluto.