Caimans and Alligators belong to the same family and so share similar features. This make the two animals have almost same differences when compared to crocodiles.
It’s sometimes argued that the Spanish word for alligators is “Caimanes” which makes “Caiman” more of a synonym for alligator and not necessarily a different species.
The most apparent difference between crocodile and caiman is that of their snouts.
Crocodiles have narrow and longer snout (takes a V shape) compared to caiman which has a much shorter and wider (U shaped) snout.
As found in alligators, the teeth of caimans is closed in when the mouth is closed while that of the crocodile are interlacely displayed outside their mouth giving the animal a grinning look.
Crocodiles are larger than caimans with some crocodiles growing up to 23ft in length. Although the black caiman can grow up to 20ft in length.