Water is your body's principal chemical component and makes up about 50% to 70% of your body weight. Your body depends on water to survive. Every cell, tissue and organ in your body needs water to work properly. For example, water: Gets rid of wastes through urination, perspiration and bowel movements Keeps your temperature normal Lubricates and cushions joints Protects sensitive tissues Lack of water can lead to dehydration — a condition that occurs when you don't have enough water in your body to carry out normal functions. Even mild dehydration can drain your energy and make you tired.