Listen to MissPrissy.
I had 2 mallards last year & hope to get some ducks this year. We raised the ducks w/our chickens and they are really messy. Water everywhere. Even if the chickens and ducks get along you're going to have slimy dirty water that has to be cleaned up a couple times a day. The chickens will drink that dirty water and poss. get sick. Even if you just use a standard waterer, the ducks will get their bills in it and suck it/gum it all up in no time at all. We had the drakes fighting w/the rooster for dominance, pulling the hens feathers out ect. They were good boys but once they reached maturity . . . uck! We won't be housing the ducks with the chickens anymore.... too much mess and too much stress. If I had one female duck all by her lonesome I would house her with the chickens for the sake of company but that would be it.