I have been hearing a pretty loud alligator at night in the lake behind the house. No crocs, though.
"...So, now you have an idea of how crocodiles can run. But how quickly can they run? 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. In these cases, the crocodile is running away from a threat - only certain extinct species of terrestrial crocodyliforms regularly hunted using a similar gait, which perhaps explains its origins.
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 (see photo). Adult males and females defending their territory or a nest may pursue an intruder, but this is normally over a short distance until the intruder has retreated a sufficient distance. Be aware that crocodilians are not the sluggish creatures they are often portrayed to be, and can move very rapidly when they need to. However, they can not run around at speeds most cheetahs would be proud of."
http://crocodilian.com/cnhc/cbd-faq-q4.htm