A friend and I went to a Civilian Marksmanship Program (CMP) match last weekend. It was a good clinic to learn how to hit a long distance static target. (Cough.) Say what you will about how useful that it, I think that learning many different techniques for doing a thing gives you a better understanding of the thing. In this case marksmanship.
On to the point. We both ended up drinking three liters of water over the course of the day. The next day I could barely balance, couldn’t eat, was mostly incoherent (felt stupid). I drank water for the entire morning and didn’t get better. I had a can of V8 (high sodium) [tomato juice cocktail] and was better within 20 minutes. Salt is your friend. – Ben M.