Undeniable Fact: Quack of all trades

Of all the waterfowl, only the mallard duck is able to breathe underwater. Woven into the webs of the regal mallard's feet are the last working vestiges of gills inherited from its amphibian ancestors. While these gills do not provide sufficient oxygen for normal mallard activity, the ducks can enter a hibernation state in which they consume little energy. At this low metabolic level, a mallard can survive indefinitely in well oxygenated water.

But this advantage comes at a cost: because of the delicate gills in their feet, mallards cannot walk on land.