We ususally take two bottles of water each on board, mostly for the bottles. (We use the fitness center alot.) The ship's drinking was is filtered as well as any bottled waters. (Hubby works in the water industry so I trust his judgement.) I also take a few bottles of iced green tea for hubby to have in the room because that's his preferred beverage. The cruise lines only seem to get cranky about alcohol, but that's a whole other thread.