This means that if they swallow too much salt, they can excrete it through their tongue. The Alligators and their Caiman relatives do not have salt glands so they are restricted to fresh water. The Estuarine crocodile has been found up to 1,350 kilometres out to sea. Even when their mouth is closed you can see all of their teeth. Alligators are not always smiling because when an alligator closes its mouth, you can't see all of its teeth.
Some people believe that the jaws of crocodiles and alligators move differently.
This is not true. All vertebrate animals, including crocodiles, have jaws with the same movement. The skull is joined to the spine and the bottom jaw moves on a hinge to open and close the mouth. The size of a crocodile depends not only on age, but genetic and environmental factors. Some crocodile environments may have more food available and a more favourable climate than others.