PLEASE ANSWER QUICKLY! Have you ever spent a hot afternoon playing ball with your friends? Or maybe you've run around the park with your dog? Bet you were pretty sweaty and thirsty when you finished playing! Maybe you were even thirsty enough to guzzle an entire gallon of water. That thirst was a sign of dehydration. Dehydration means that your body is losing more fluids than it takes in, and that's not good for your health! Don't depend on your thirst to tell you whether or not your body needs a refill. Make sure you drink water a few hours before gearing up for physical activities, and keep drinking after you're done. Be smart and stay hydrated!