1. Water is crucial to helping your body maintain basic functions, from breathing to brain function. To break it down, your body is between 53% and 65% water (the people with 53% water tend to have more body fat.) Your brain is 70% water and your lungs are even more fluid, at 90%. Without water, you’ll start to notice things like bad breath, dry skin, tiredness, fogginess and sugar cravings, and chronic dehydration can even result in kidney stones and bowel disorders. Signs of dehydration include a dry mouth, headaches, dizziness and low blood pressure.