I have a pair of Cayuga ducks, and they free range with all my chickens. For a time they also slept in the chicken coop in their own corner, but the ducks seem to be more nocturnal - on patrol at night - so they stopped going into the coop before the auto door closed.
I keep 3 pools for them: 1) a kiddie pool which the chickens appreciate the coolness around it from the ducks splashing, and they drink out of it, too. 2) a 40 gallon rubber horse trough, which the chickens drink out of and the ducks dabble in it, sometimes swimming in it. 3) a 300 gallon stock tank in which they occasionally swim if I pick them up and put them into it. They don't trust the ramp up to its edge. I'm gonna have to make a different ramp, eventually, I think.
I feed grower/finisher to the entire flock and offer crushed oyster shell free choice, which the duck uses, too, as she lays a nice egg every day.
Everybody gets along, even eating out of my hand together. Not sure how it would work with more ducks, though. (We'll see in the Spring, as I think I'll incubate some duck eggs then....)