It’s in every living cell, tissue and organ, and it’s second only to oxygen as the thing we need most to survive—pure, clean water. We can’t live without it, and we can’t live well without enough of it. We are constantly in need of water as we lose water with every breath and every activity of the body. We are especially at risk for dehydration when we exercise or we are ill—this is when dehydration, even mild dehydration, can take its toll, causing you to feel tired and drained of energy. Anyone may become dehydrated, but young children, older adults and people with chronic illnesses are most at risk.