Water exists in many places in the universe and May be the principal element for life On Earth's surface. Its presence is a hallmark of the habitable zones for living things (humans, animals, and plants). About 70 percen...Water exists in many places in the universe and May be the principal element for life On Earth's surface. Its presence is a hallmark of the habitable zones for living things (humans, animals, and plants). About 70 percent Of Earth's surface is covered with water, but only about 1 percent of the water On Earth's surface is usable by living things (groundwater and surface water).