- They have spread all around the tropical parts of world (Alligators and Caimans are subspecies of the Crocodile);
- They are the most dangerous freshwater predator on the planet;
- Since they can tolerate salt water they have ventured hundreds of miles out to ocean looking for new islands. This makes them a threat to any living thing anywhere there's water (several are found in Austin's Town/Ladybird Lake each year);
- They have a protective membrane (like swimming goggles) that closes over their eyes when they are underwater;
- They have perfect poise and submarine-like control when underwater. Here are pictures of one descending underwater without any visible movement of its body:
Alligators, which are what we have in North America, are astonishingly powerful swimmers; humans stand no chance of out swimming them. They are also, though, very fast on land. I have done some research, and there are two schools of thought for escaping on foot from an alligator. The most popular notion is that, since alligators are capable of bursts of speed but allegedly not so agile when running, you can put distance between you and the alligator by running in a zigzag pattern.
Several other websites I consulted dispute the wisdom of this strategy, though. Alligators can run up to 20 mph, but only for 30 or so feet. After that they get tired and slow down considerably. As long as you have a 10 or 15-foot head start you should be able to escape by running in a straight line.
Alligators attack by surprise, though. They launch themselves from the shallow water or vegetation they have been using as camouflage. For Christ's sake never feed an adult alligator and if you ever encounter baby ones get the fuck out there as quickly as possible. The mother is nearby and will respond fiercely if she hears distress calls from the youngsters.
If an alligator actually gets its mouth around you, your best bet is to fight it off. In spite of the tough-looking skin alligators are very sensitive to touch. You will not be able to force its jaws open, but if you bash it on the snout or in the eyes it may relent.
It is critical, though, that the alligator not start rolling or spinning. Alligators can't move their jaws from side-to-side; they tear meat by holding it in their jaws and rolling over repeatedly. The best way to prevent the alligator from doing this is to somehow immobilize its tail. If some part of your body is in its mouth, though, you obviously will not be able to do this yourself.
The reassuring news is that in spite of how well some movies (see below) play on rational people's fears, alligators probably do not live in our sewers.