Living without water is a very different story. We constantly lose water through sweat, urine, breathing and other activities. If it is very hot your body can dehydrate within a matter of hours. The water and minerals the body loses must be replaced so that our organs can work as they should. Water helps us cool down in the heat; otherwise we would suffer from a heat stroke. Doctors also tell us to drink a lot when we are ill and have fever.
Dehydration can lead to many illnesses, from too little urine to a dry mouth, a fast heartbeat or even vomiting. Shock comes at the end of dehydration. The body becomes cool and blood pressure goes down rapidly.
Doctors recommend drinking one to three liters of water a day, depending on the climate and how much you sweat or exercise. You should never go on without water for a day or more.