Crocodiles are cold-blooded predators that have existed since ancient times. Crocodile's physique has only slightly evolved. Crocodiles usually live in fresh water waters such as rivers, lakes, swamps and other wetlands. There are also crocodiles that live in brackish water such as estuarine crocodiles.

Crocodiles are entirely carnivorous and have the most potent stomach acid of any vertebrate animal, so they are able to digest bone and shell.

Crocodiles usually prey on fish, birds, mammals and other smaller crocodiles. Crocodiles have a heart with four chambers, a diaphragm, and a cerebral cortex.

Crocodiles generally inhabit freshwater habitats such as rivers, lakes, swamps and other wetlands. Crocodiles have a peculiarity, that is, they will stay still while sunbathing or in the water, and will move quickly when there is a threat or a prey is approaching.