There are three main “gaits” (styles of locomotion) that describe how crocodilians get around on land. The “belly crawl” is typically a fairly slow gait in which the crocodile slides over a slippery substrate such as mud, using its legs to push itself along on its belly. However, this gait can be modified to shift that bulky body at impressively high speeds, normally away from a threat. “Belly run” becomes a more appropriate description of this faster gait, where the legs still operate on either side of the body rather than from underneath it.
The next gait is the “high walk” […] which is uniquely crocodilian - resembling the erect gait of a mammal with the legs directly underneath the animal, rather than the splayed gait of a reptile. This is a slow means of getting around, but it is very useful for picking the bulky body off the floor to negotiate obstacles or to avoid the friction induced by scraping the belly against non-slippery substrates such as soil or rock. […]
When moving quickly away from a threat, crocodilians employ one of two methods on land. The first is the faster “belly run” which I’ve already mentioned, in which the legs move very rapidly in a typically reptilian pattern to propel the crocodile forward. […]
The second rapid locomotory gait on land is called “galloping” […] The form of this gallop is quite unique, with front and hind limbs moving as synchronous pairs. […]
Most crocodiles can achieve speeds of around 12 to 14 kph for short periods, which is somewhat slower than a fit human can run. Don’t believe the hype - if you’re reasonably fit, you can definitely outrun a crocodile! Even faster are galloping crocodiles, and Australian freshwater crocodiles have been clocked at just over 17 kph over distances of perhaps 20 to 30 metres before they begin to tire. […]
However, crocodiles can accelerate much faster than this over very short distances by exploding into action - I have measured adult saltwater crocodiles (around 4 metres total length) moving at 12 metres per second for a quarter of a second, which is long enough to capture prey standing within one body length before it even has time to react. This is where crocodiles excel - launching themselves into motion from a standing start, hoping to cover the short distance between themselves and their prey before the prey can react. This isn’t running, however, because the crocodile cannot maintain this acceleration for more than a very brief instant.
Bear in mind that crocodiles do not normally chase their prey - their typical hunting strategy is one of surprise, lunging at prey and capturing it in a single fluid movement. Secondly, crocodiles have a relatively low stamina and their physiology does not permit sustained exercise. When a crocodile runs, it is nearly always away from a potential threat and into the water […]