Crocodiles are mainly inhabitants of swamps, lakes and rivers. They are tropical reptiles found in Asia, the Australian region, Africa, Madagascar, and the Americas.

The estuarine (or saltwater) crocodile lives almost entirely in the ocean and may swim miles out at sea. In wets Africa the dwarf crocodile is found mainly in the rivers of the forest region.

Copulation occurs in the water and lasts about 10 minutes, for crocodiles. It is followed by courtship whereby they rub their muzzles against each others and over the necks. The male then mounts the female on the back, and both animals rotate their tails so that the bodies receptive openings are brought into contact.

They lay hard shelled eggs which may number upto 100 depending on the age and size of the female crocodile. The female builds a nest for the eggs in the form of a trench or mud mound. The eggs hatch after 2 or 3 months and the young are fully developed. The female removes the dirt and debris from the nest, After hatching the female does not provide any further care for the young.

The crocodile is adopted to its amphibious way of life. The elongated body with its long, muscular paddle tail is well suited to rapid swimming. The external nostril openings, the eyes, and the ear openings are the highest part of the upper side of the head. Hence, they remain above the surface of the water even when the rest of the head is submerged.

Crocodiles have eyes with vertical, slit-shaped pupils. These narrow in bright light and widen in darkness, thus controlling the amount of light entering the eye. The upper surfaces of the back and tail are covered with large rectangular horny plates arranged regularly in longitudinal and transverse rows.

The back, belly and sides of the body have small knobby scales. The legs are short but powerful. 

The crocodile's flat snout is usually quite long. The outer margin of the jaws in most species is jagged. Each jaw carries a row of sharp teeth which are replaced continuously. mouth floor is thick with a fleshy tongue which is firmly attached and virtually immobile.

The young crocodiles about to hatch from the eggs utter squeaks signaling they are ready to emerge.

The extent of the crocodile is defined by its loud vibrant roar. Crocodiles are capable of deep grunting sounds and a warning hiss.

Like other crocodilians, they are long-snouted, lizard like, and carnivorous. Crocodiles have narrower snouts than alligators, and the fourth tooth in each side of the lower jaw is visible when the mouth is closed. They are reputed to be livelier than alligators and more likely to attack humans. Alligators, like other crocodilians, are large, lizard-like animals with powerful tails that are used both in defense and in swimming.

Their eyes, ears, and nostrils are placed on top of the long head and project slightly above the water when the reptiles float at the surface, as they often do. Alligators differ from crocodiles in having broader snouts; in crocodiles, moreover, the fourth tooth in each side of the lower jaw projects outside the snout when the mouth is closed. The Mississippi alligator is black with yellow banding when young and is generally all blackish when adult. The maximum length is about 6.8 metres (19 feet), but it more typically ranges from about 1.8 to 3.7 metres (6 to 12 feet).