The axolotl (Ambystoma mexicanum), also known as the "water monster" and the "Mexican walking fish," is a peculiar but versatile foot-long (30-centimeter-long) aquatic creature that can use its four stubby legs to drag itself along lake bottoms, or else swim along the surface. It also has a strange, lizard-like face with plume-like gills and a mouth that seems to curl into a smile.
Even so, the axolotl, which feeds on aquatic insects, small fish and crustaceans, doesn't have a lot to be happy about these days. The fish is indigenous to the Xochomilco network of lakes and canals around Mexico City, but those waters have become so polluted due to urban sprawl that a 2013 study from Mexico's National Autonomous University failed to turn up any specimens after four months of searching. While axolotls survive in aquariums, water tanks and research labs, scientists are still hopeful that axolotls haven't completely vanished in the wild [source: Associated Press].