I agree ducks are wonderful! The messy water can be a pain, but I never met a chicken that kept the waterer sparkling clean either LOL.No. No. No.
Ducks are awesome!
They do mess up their water and like to splash it everywhere, but they are lovely animals to have. I'm letting ours out on the lawn this year during the day. That should help to keep them from being so messy in the run as they'll spread out more. I've also learned some things in my ducky journey. Raise their pond, filter their pond, use bedding in their run that can be composted later. These steps help make ducks less of a messy to own and aid in keeping them healthy.
As for slugs and snails, ducks LOVE them. I only get small slugs about 1-1.5" long. I've never seen a large slug here. The ducks eat any creepy crawly they can get though.
I can’t imagine keeping them in a run, that would be a LOT of work. My flock tends to run the big yard in the morning and then they go to the side yard for the warm part of the day where there’s more shade and it’s cooler.