I keep my 9 chickens and 2 ducks together, in the same coop and run. The chickens are the first to go into the coop at night, but both of my ducks also put themselves away each evening. The ducks are a bit messier... which only means I completely change out the litter in their area of the coop about twice a week. Mostly, just because it gets wet. My ducks do have access to food and water during the night in the coop, and yes, they love to play in their water.
I had originally planned on building a separate duck house/run, but have decided against it as everyone does so well together. LOL, that way I can use the large, covered, dog run that I bought for the ducks for some turkeys in the spring!
I do keep the duck "pond" (a large, shallow livestock trough) outside of the run. When I open the run door, the ducks waddle out to the trough, swim a bit, then head back to the run on their own. Good little duckies that they are!
I love watching the antics of the chickens and ducks together... twice the fun!