Duck+water= Giant Mess!
I had some luck cutting down on the mess by using a bucket and putting a board on top that was attached so they couldn't knock it off. They only had enough room to stick their heads in, and a lot less water splashed everywhere. Also I used an old dog kennel tray to keep the splashes somewhat contained.
Also, when keeping them with chickens they make a huge mess if you are using a typical chicken waterer. If possible, I would put the chicken water out of their reach, where only the chickens can get it. Or even better, use a waterer for the chickens that has those chicken nipple things in it. You can build a pretty simple one with a 5 gallon bucket. Those are so nice (for keeping down chicken mess and duck mess!) You will still need to have a bucket for the duckies since they need to wash the bills out.