Crocodiles are superbly adapted for an amphibious life. They can remain underwater for up to an hour and swim rapidly using their powerful tail. On land they usually 'high walk', where the limbs are held upright close to the body. Fast movements usually involve a sprawling waddle or a quick slide down a muddy bank. The Australian Freshwater Crocodile (Crocodylus johnstoni) grows to 3 metres long and can gallop. This gait allows it to escape predators and jump over obstacles between it and the water. It can reach speeds of up to 18km/hour but becomes exhausted very quickly, so can only gallop for short distances.