There are five major requirements for life. Without these things, life as we know it would not exist on the planet. Because life must obey the physical laws, especially those of thermodynamics, energy is important. Without energy organisms could not grow, reproduce, or even maintain their shape.
Water plays many roles in life.
It provides a mechanisms where by heat can be dissipated, and it also provides a means of transporting materials because of its ability to dissolve many compounds. However, one of its most important roles is in changing energy from one form to another. Without water, plants would not be able to trap the energy in light, and animals would not be able to process the energy in their food. The energy from the sun is not in a form that can be directly used by organisms. Organisms require energy in the form of chemical bonds.