They are from the same species of family. Caimans have more rounder mouths, crocodiles faces are longer.
Are these hatchlings restrained? It appears they are in a glass tank or at minimum restricted behind glass panels. The reeds are pushed flat, the surface of the water in the background is straight and the 'glass' seems to be dirty on the far right hand side below the hatchlings jaw. If so, very poor form National Geographic.
This photo is awesome in so many ways, and props to the photographer for getting this shot. It must have been hard to have taken, because the water looks pretty shallow.
@Matthew Buchannon , thanks for your comment. This picture is was taken in a completely natural condition . The "glass" you've mentioned is the dome port of my underwater housing and the animal are in a natural habitat. I've learned from experts that in the first week of life baby caimans have slow reactions and in this conditions it is possible to get close. But it is very difficulty to find since, as you pointed out, the water is very murk and full of particles. Actually it took me two weeks to find this good condition to take this picture. I traveled to a place with hi concentration of nests, in a remote location if Pantanal wetlands of Brazil. And there is also the "mother" who stays around to protect the newborns. I think that capturing the animals and put then in a aquarium as you mentioned would give a better (clean water) result . But it is not journalism. Actually, the yelowish water and particles mach perfectly my emotional response to these in front of this story. Hope it can help to explain your doubts.
@Matthew Buchannon It has nothing to do with National Geographic. They would normally live in the same, muddy type environment. Too clean an environment would not make them immune when they are released... if they are in a tank.