when we stayed at the wl, there were ducks every morning in the pools. at the AKL, the lifeguards were telling children who were getting too close to a mamma duck and her babies who were nested in the bushes right next to the pool to get away from the ducks... these ducks swam in the pool (not when everyone was in the pool). at the GF, the ducks were in the quiet pool when people were in it (they were probably very used to people), and they were hanging around the bar area right next to many people. they were sort of 'guarded' by the cm's (again, telling kids to leave them alone, etc). I just remembered that we had our goggles and were swimming underwater near them, watching their little webbed feet paddle, and it was just the cutest thing. but i have thought about them getting germs in the water, but i guess people can put just as many germs in the pool too (too many parents not putting swim diapers on the babies - i saw on our recent trip... yuk!)
so yes, they are there. just remember how much chemicals disney uses to keep the pools clean (our swimsuits are always eaten away and/or totally faded by the end of our trip by the chemicals). and again, there are many babies without swim diapers in the pools unfortunately.