I would swim in a pool that ducks swim in, no problem.... The filter medium will take care of the organic matter and the chlorine will take care of the bacteria...the chlorine will take care of the ducks too though...
The pool company is not really worried about contaminating their equipment...they just don't like cleaning up after the ducks...They get a set fee to maintain the pool...if they can walk up to one pool, turn on the vacuume, shock the pool and leave, but the next one they have to spend extra time vaccuming and have to hose off the deck for the same money as the first......Pool companies don't ever have a problem with babies in diapers in pools and god knows baby diapers are worse than a few ducks....