Your answer will depend on how you look at it. You can look at water's qualities and how they serve life, or you could look at life and what it would be without water. It also depends on how much detail you want to go into. For example: Look at the main quality of water—it's liquid. What do liquids do? They transport things. They soften things. They cushion things (and more). What other qualities does water have? Answer each one for a general look at water.
If you want to go more detailed, then you could ask: What does water transport? Big things like trees and houses in floods, down to tiny things like cell wastes, food, and oxygen. In what situations, i.e. who or what benefits most and when? And do the same thing with each of your more general questions.