All ducks like a pond to swim, or at least have a bath and splash in, but they don't necessarily need to have one. If it is a small pond they will make it very dirty very quickly, so its often best to get one you can empty out and refill. Large breeds need water for successful mating, but smaller ones can generally manage without. If they do not have a pond make sure the water is deep enough for them to wash their eyes and beaks in.
If you haven't kept ducks before you will be surprised at how much mess they can make, but they are interesting to keep and fun to watch, and they should keep a smallish garden free of slugs, though they will eat some of your plants such as lettuce and hostas to name a couple.
Khaki Campbell were specifically bred to be run with chickens, so they are a bit cleaner, and do not need swimming water. They lay prolifically, and for some years held the record for eggs laid per year. Duck eggs are excellent for cooking, and you either like or dislike them for eating - I personally don't like them to eat, though will cook with them.
I keep giant Rouen, which I like because they are quieter than most ducks (call ducks and some of the smaller breeds of ducks can quack incessantly) They are good foragers, and can be very friendly and full of character if you spend time with them. But there are many varieties to try, all with their different qualities.
All the best
Sue
Dark Brown Eggs