The World's Greatest Water Filter (I'm convinced) was designed and installed in each and every duck! We bought three ducklings this spring, and unlike our chickens, they will drink any water-- no matter what it looks like.
Chickens are a bit pickier, and who can blame them? I prefer clean drinking water myself, but DUCKS... they swim in it, bathe in it, and then take a slurp. At first, I was worried it may harm them (showing my ignorance of ducks when we brought them home), but that's certainly not the case.
We are about to purchase a water filter for our home. I came in a couple of days ago and commented to my wife that the ducks must come equipped with a Royal Berkey! In case you don't know about the Royal Berkey, it is a water filtering system that sits on your counter-top and filters H2O much better than the filters in our refrigerator or filter pitcher. In fact, the Berkey will make ditch water drinkable! You can read more about it HERE.