Saltwater crocodiles can be dangerous (and very aggressive) to both humans and other animals. They can move very fast in the water and on land. Sometimes, they can kill a person, but this does not happen very often. Usually, there are "No Swimming" signs near areas with high crocodile activity. Crocodiles can lie very still for up to one hour. They are able to leap as high as . In March 1987, a Toyota land cruiser collided with a crocodile at Cahill's Crossing on the East Alligator River. The crocodile knocked the motor car off the roadway with its tail. Crocodiles can also live in fresh water. Scientists have found crocodiles up to 235 kilometres from the sea.