In real life, crocodilians (crocodiles, alligators, caimans, and gharials) are amphibious, persistent carnivores. The largest reptiles of the modern world, and second only to the dinosaurs, they are among the most fearsome apex predators in the animal kingdom. While mammalian predators are viewed more positively by humans, crocodilians tend to be judged by their history of public attacks.

Painting crocs in a negative light, stories double down on their predatory nature and portray crocodiles as hostile threats lurking in rivers, swamps, and sometimes in castles' moats or sewers. This trope works with both ordinary and anthropomorphic crocodilians; while regular crocs will be portrayed as bloodthirsty killers that attack on sight, Funny Animal or civilized crocodilians will be presented as nasty, cruel, and very vicious. In cases where the latter is not villainous, they'll still be thuggish bullies. Sometimes, crocodilians may feign emotion, alluding to the infamous Crocodile Tears, in order to lure in unwitting victims.

The reason why crocodilians are treated as callous monsters boils down to their role as apex predators: they're not only able to hunt mammals up to the size of a one-ton buffalo, but they are also the only predator (besides humans) capable of actively hunting top-order terrestrial predators like big cats. Crocodiles in particular have the most powerful bite force of any modern animal, capable of crushing turtle shells with ease. Most notably, crocodiles cannot chew their food; instead, they rely on a technique called the "death roll", the practice of turning themselves along their longitudinal axis while clinching their prey in their jaws in order to rip out chunks of flesh they can swallow whole.

Of course, reptiles as a whole don't have the best reputation in general, but crocodilians are prime targets of this portrayal because of how monstrous they look: the lack of lips result in their jagged teeth always being exposed and make it look as if they are perpetually grinning, and their bumpy, rugose scales give them a far more dinosaur-like appearance than other reptiles, evoking the theme of a Prehistoric Monster. Extinct members of crocodilian genera, which were gigantic beasts like Deinosuchus and Sarcosuchus, fully embodied this concept, while spinosaurs were also seen as a parallel due to their crocodilian snout and role of a river-dwelling predator. Although this can apply to many crocodilians, crocodiles are more likely to be portrayed as savage than alligators, possibly due to the fact alligators are comparatively less aggressive towards humans (which also applies to most crocodile species) and also slightly less threatening looking (gators are smaller and have more rounded features and overbites, while many crocs are very angular and all of them have toothier grins^note though ironically, gators have more teeth than crocs), though they are still prone to this trope.

As with most carnivore portrayals, in reality, crocodiles aren't as hostile or one-note brutal as fiction portrays them to be; they rarely hunt frequently, and at the longest, they've been known to go up to a year without actually eating anything. Instead, they generally spend their time basking in the sun most of the year or burying themselves in dirt and mud during winter.

Sub-Trope of Reptiles Are Abhorrent. See Snakes Are Sinister and Malicious Monitor Lizard for other villainous reptiles. See also Threatening Shark, Savage Wolves, and Bears Are Bad News. For another river-dwelling menace, see Angry, Angry Hippos. May be invoked as a Monster in the Moat. See also Colossal Croc and Sewer Gator, which this trope may overlap with if the crocodilians are hostile and actively trying to kill the characters.

Examples: