ALL mallard based (Non-muscovy) ducks will poop up your pond pretty quickly. I have a mixed flock (15) and they turn a 7500 liter swimming pool into
in 3-4 days. The amount they swim is dependent on the duck more than the breed. If you want your pond nice, I suggest you fence it off from them then either keep them out or you regulate when they are allowed to swim. A duck NEEDs water it can submerge its entire head in so it can clean its nares and eyes (buckets work nicely), but it will take advantage of any water it can find (and will dig holes if that water is in dirt). So any duck can live a happy life without much access to "swimming" water, but they like swimming more
They are also very happy being sprayed by a garden hose in warmer weather.