Now they are so numerous in Florida that they are sometimes destroyed as nuisances. The problem is that most people can't tell the difference between the two species. On both sides of the lower jaw of crocodiles, the fourth tooth from the front of the snout is visible when the animal's mouth is closed. When an alligator's mouth is closed, you can't see any of its lower teeth. Alligators have a broad snout.
Crocodiles have a narrow snout.
Alligators' coloring is darker than that of crocodiles. If you hear one of these big reptiles bellowing, it's an alligator. Crocodiles don't bellow and are far less vocal in general. That way, the crocodile won't suffer from so many cases of mistaken identity. The American Museum of Natural History.