Episode Five of the BBC's Life of Mammals features The Meateaters -- the various cats and dogs who hunt for their sustenance.
My favorite among these predators, and one that's probably the most rare, is the South American Bush Dog. It is the only member of the dog family that has webbed feet. The St. Louis Zoo, which I've visited, has bush dogs, and their web site's South America page (from which I got the photo here) includes a short video of one swimming. You can also get much more info about the bush dog from Wikipedia's article, which has some good external links.
Other highlights from the episode: