The Yard Bandit - are and eat snails, insects, and mice. They love to get into your garbage for a few morsels. To discourage a possum, keep the lid tight on the garbage can and keep bushes and other foliage in the yard trimmed back.
The owners of this pen say that they really like the lobed-shape of their pool because the ducks can swim in their own areas. Based on their other photos, I don' think they have a drain, so they have to lift the whole thing out when they need to clean it.