It makes a world of difference in terms of recovery, energy level, and even bowel movements.
I really need to drink more water.
I remember some days in Afghanistan where it was usual to take in about 10-12 liters of water a day.
I need to note that I do have one or two cups of black coffee in the morning so it's not a complete water-only intake.
Black coffee is excellent for your health. I consume plenty of it, I just don't balance it with water like I should. I remember drinking about 4-6 liters some days in Iraq, but I worked the night shift and my deployment was half during the late winter/spring so I didn't get exposed as much to the searing heat of the summer.