No, but it helps. Drinking water keeps you hydrated, which prevents you from retaining fluid.
Drinking a glass of water before a meal can help fill you up, so you won't eat so much.
What size is a glass of water is it a half pint ?
Yes, it's generally accepted that a glass of water is one cup (8 oz or 1/2 pint).
Many recommend 8 - 8 oz glasses/day. New studies show there's no set amount, but you should drink often enough to prevent dehydration.
By the time most of us "feel" thirsty, we're already starting to dehydrate.