Hyponatremia . We called it hyponatriosis or 'water-drunk' in the army. We had a girl in our platoon over-hydrate and go floppy on a march, and my swear-to-god buck-oh-five bunkmate had to play crutch for the rest of it while we all redistroed all their collective gear. (calm your breathing: they marched in back with the medicos under obs the entire time, and we didn't fail the little exercise we were on, and it was her choice to continue at every stage, and she was lauded for it afterward. This is a heroism story.)