My male pekin duck was by himself for a bit with my chickens, then he started to mate with my hens, my rooster was losing his mind. So I got 2 female muscovy ducks, 1 female he was too aggressive in his mating and it was hurting her. 2 is just right for him.
They have a pond in the summer but winter when it's too cold to keep unfrozen I take it away and keep a manageable water container out there so I can change the water easily 2 times a day when it freezes or gets dirty.
My ducks now have their own night time pen ( free range during the day ) but they lived in the same pen with my chickens for about 3 years fine. Well, other than the time my pekin didn't have a lady friend. I prefer to keep them separated for cleanliness, water needs are different, eating styles are different. It just made my life easier and their lives so much better to be in their own areas. It just took time and money to make it happen, but they did live fine together and I do have a rooster. Hope this helps a bit.