While closely related, crocodiles and alligators feature a variety of differences. The easiest way to tell is that alligators prefer freshwater, and crocodiles prefer saltwater though both can tolerate the reverse. Crocodiles tend to show their teeth when their mouth is closed, and alligators have shorter heads. Alligators are more tame, while Crocodiles can be very aggressive even to zookeppers who’ve tended to them for years. Alligators are native only to America except one small exception for a species in a tiny part of China.