I've never had a problem with the water on an NCL ship, but then, I'm not much of a water snob. I do remember Carnival's water having an odd taste but not so with NCL. I always have a travel bottle stashed in my backpack and fill it when leaving the ship rather than buying $3 bottles of Evian. Water is always available at shops on the pier for less than onboard in case you've forgotten to fill up.
If I remember correctly you can rent walkie-talkies onboard. Although I find them annoying, I'm also not trying to corral a group of teens either. Might be something to think about bringing or renting.
As you know there is as much to do as you can squeeze into a day, but just choose wisely and remember it's about relaxing, not winning the scavenger hunt!