Water helps your kidneys function properly. When they aren't able to work to their capacity, your kidneys pass on the work to the liver. But your liver is supposed to metabolize fat into energy, and it doesn't have enough time to do that if it's working for your kidneys. This causes less fat to be metabolized and more to remain in the body. By increasing water intake, you can reduce the size of fat deposits in your body.
Water also acts as a natural shock absorber for the eyes and spinal cord.
When you don't drink enough water, your body does its best to hold on to every drop. That water is stored outside the cells, giving you swollen hands, feet and legs. Increasing your water intake can also cure water retention caused by excess salt. Water passed through the kidneys removes extra sodium from your body. Water is a great thirst quencher while other drinks can actually contribute to dehydration.