Just bring or buy a large sports bottle. The water on the ship is quite good. I usually drink bottled water, but was quite satisfied with this. Tap water on board is purified.
Laura
PS... water on ship? Is ok, if your use to city water (which I'm not....so the chlorine really killed the taste of tea's and coffee's.... )
Note: they produce their water by evaporation of sea water...and just because the pool is filled with sea water, does not mean that its going to be as rough as the ocean lol, (this was a comment from one passenger to another)