Crocodiles are large reptiles. The Australian saltwater crocodile grows up to seven metres and is extremely dangerous. Crocodiles lurk in swampy waters from which they suddenly lunge out to snap at their prey. They feed on fish, mammals and birds. After they eat, crocodiles sometimes swallow a couple of stones to improve their digestion. Their tail allows them to move swiftly both in the water and on land. Some species rank among the world's largest reptiles because they measure almost eight metres. Yet other species do not grow longer than 1.8 metres. Crocodiles can live up to 100 years. They are no threat to humans, but have become endangered by humans for they are hunted because of their skin, of which wallets, shoes and handbags are made. In some countries, crocodile meat is considered a delicacy.