Lots of people tend to not drink enough water/fluids. That seems to be changing, as carrying bottled water has become popular.

Just a word of caution: It is possible to drink too much water. Excess water intake can over-dilute the blood and lead to seizures (because of salt content in blood becoming over-diluted.)

Also, people with weak hearts can get fluid overload that leads to back up of fluid in the lungs. It's good to check with your doctor, who knows you, about what is a good quantity to take in. Plus, what is a good quantity one day may not be the optimal intake on another. That can very according to activity level and heat level in the environment and other things.