From the nestle corporate website:
The body fluids contained in the different compartments perform the following important functions:
· Carry nutrients and waste products.
· Vital to the life and shape of every cell.
· Participate actively in many important biochemical reactions of digestion and metabolism.
· Assist with temperature regulation, i.e., cooling the body by evaporation from the skin as perspiration (sweating).
· Act as a lubricant around joints.
· Serve as a shock absorber, e.g., for the brain and the spinal cord or inside the eyes; in pregnancy, the amniotic fluid around the growing foetus provides protection against shock.
· Serve as a solvent for minerals, vitamins, amino acids, glucose and many other small molecules.
Nestle Corporation
There's more on the subject of water at the above link. It's very brief, but it's pretty good.