Water (chemical formula: H2O) is a transparent fluid which forms the world's streams, lakes, oceans and rain, and is the major constituent of the fluids of organisms.
See Below:-
1-Composes 75% Of Your Brain

2-Regulates Your Body Temperature

3-Helps Carrying Nutrients And Oxygen To Your Cell

4-Moistens Oxygen For Breathing

5-Makes Up 83% Of Your Blood

6-Helps Convert Food To Energy

7-Removes Waste

8-Proctects And Cushions Your Vital Organ

9-Helps Your Absorb Nutrients

10-Composes 22% Your Bones

11-Cushions Your Joint

12-Makes Up 75% Of Your Muscles.
Source:-http://asifawalesblog..com/2016/06/12-importance-of-water.html?m=1