All living things need water to survive. Without water, the human body stops working properly. Water makes up more than 50 percent of your body weight and a person cannot survive for more than a few days without it. Water flushes toxins out of your organs, carries nutrients to your cells, and provides a moist environment for ear, nose, and throat tissues.
Water is also in lymph, a fluid that is part of your immune system, which helps you fight off illness. You need water to digest your food, to get rid of waste, and to sweat. Too little water in your body leads to dehydration, and it can make you tired and unable to function. Your body gets water from drinking it, but lots of foods, such as fruits and vegetables, contain water too.