drinking too much water doesn't actually cause water weight, it's actually quite the opposite. you retain water when your body either isn't getting enough water (it thinks it needs to conserve) or if you're taking in a lot of salt (the water's retained to balance out the sodium).
drinking a lot of water actually keeps water moving through (and out of) your body - if you're a sparse drinker, and take a few days drinking a *lot* you'll actually lose a few pounds of water weight.
i drink liters and liters a day - a bottle is always on my desk - and i've found no connection to D. if i drink *way* too much at once it can make my stomach feel off like eating too much - full is full. but now that i'm used to so much water, i get headaches if i don't drink enough. (with donnatol i need even more.) and what they say about hydration and your skin is definitely true.