People often confuse crocodiles with alligators. In contrast to the blunt-snouted alligators, crocodiles have a tapered snout. The fourth tooth on each side (counting outward from the centre front) of the crocodile's lower jaw fits into a corresponding pit above that is open to the outside, so the teeth stick out when their jaws are closed.

Fourteen species of crocodiles are recognized (as of 2008); depending on the species, crocodiles vary in size ranging between 1 and 10 metres in length (3 to 33 ft.). Crocodiles larger than 3 metres long (10 ft.) have no enemies apart from humans.

Crocodiles eat fish, birds and mammals, including the occasional human. Cannibalistic, they also eat each other. Because larger crocodiles will eat smaller ones, the individuals in a grouping will usually be about the same size, smaller crocodiles having been eaten or avoiding larger ones.

One species of bird called the Crocodile Bird wanders freely among the basking Nile crocodiles (Crocodylus niloticus), picking leeches and parasites from their skins, and food fragments from their mouths. They live in harmony, the Crocodile Bird providing a lookout for danger for the crocodile and a tooth-cleaning service in exchange for food.

Crocodiles are cold-blooded. Their body temperatures are only as warm as the surrounding temperature. If the temperature is high, they slip into the water. If the air is cool, they like basking in the sun, and do so in groupings, and with their mouths open. Mouth gaping is similar to the panting of a dog; it helps a crocodile cool off.

Crocodiles are found in the warmer waters of Africa, Asia, Australia, North America and South America. Some species live in fresh water, and some in salt water. The salt water species tend to be the larger ones.