Bottled water will cost you and is not usually included with a beverage card package. There will be a water fountain in the buffet restaurant, and most bartenders will be happy to fill your bottle from the bar fountain.
I pack a 20 oz plastic glass/cup in my luggage, as the glasses in the buffet area are only 6 oz. and if you request water at a bar, the glasses are only 8 oz. Not large enough to keep by your side at the pool.