Is a crocodile a carnivore herbivore or omnivore?

A crocodile is a:  "carnivore" .

Note:  A "carnivore" eats "meat" (animals) only (or primarily) as their predominant—or sole/chief food sole. 

This would apply to crocodiles.

An "herbivore" eats plant life, or even animal plankton and plank plankton (e.g. organisms that are"filter feeders" as well as other organisms) —and/or eats plants/algae/primary primary producers, as well.
 
Crocodiles diets consist chiefly of other animals as a food source; and as such would not be "herbivores" or "omnivores" (see below) — but rather, "carnivores.

An "omnivore" eats BOTH animals AND plants.