Crocodiles are scaly armour -clad reptiles that include crocodiles , alligators , caimans and gharials.These are the survivors from a prehistoric age-their relatives first lived on earth with the dinosaurs nearly 200 million years ago. Today they are the dinosaurs' closest living relatives apart from birds .Crocodiles are fierce predators. They lurk motionless in rivers, lakes and swamps, waiting to snap up prey with their enormous jaws and tough teeth. Their prey ranges from insects frogs and fish to birds and large mammals such as deer and zebras. Very few crocodilians regularly attack and kill humans. Most are timid. Crocodilians usually live in warm, tropical places in or near fresh water and some live in the sea. They hunt and feed mainly in the water , but crawl onto dry land to sunbathe, nest and lay their eggs.