Caimans and Alligators are alike. You can't really tell them apart. But their eyes can tell you which is which. An alligator's eyes are flat on their head and don't have a spike on them, but Caimans' eyes do. To tell the difference between a crocodile and an alligator, look at the snout and the teeth.
Alligators have a stumpy short snout.
A crocodile has a long skinny snout, but not as long as the Gharial. A crocodile's teeth, when it closes its mouth, its top teeth stick down, and its bottom teeth stick up. An alligator's teeth, when it closes its mouth, its top teeth stick down, but its bottom teeth don't stick up and out. Me and Gators I've only seens gators in zoos, but if I saw one in the wild, I would like to take pictures of it, and do research on it.