plants and animals (including people) are mostly water inside, and must drink water to live. it gives a medium for chemical reactions to take place, and is the main part of blood. it keeps the body temperature the same by sweating from the skin. water helps blood carry nutrients from the stomach to all parts of the body to keep the body alive. water also helps the blood carry oxygen from the lungs to the body. saliva, which helps animals and people digest food, is mostly water. water helps make urine. urine helps remove bad chemicals from the body. the human body is between 60% and 70% water, but this value differs with age; i.e. a foetus is 95% water inside.