They're faster than you are. The only way to get away from them is to zigzag because they run in a straight line and it is difficult for them to turn quickly.

they are fast in water and surprisingly fast on land. you could climb a tree, but you may get stuck there a while. running in a zig zag pattern would work. it is unusual, however, for an alligator to attack an adult unprovoked. they prefer small dogs...

"3: Stay at least fifteen feet away from alligators or crocodiles. Once you've spotted them, give crocodilians a wide berth. Fifteen feet is usually ample on land, but during mating season, it's a good idea to stay even farther away. Always stay far away from nests or baby crocodilians, as mothers are fiercely defensive. Crocodilians can produce short bursts of speed on land that can take you by surprise if you're too close. In the water, these animals are far faster than humans and feel more at home, so it's best to give them as much space as possible." "5. Run away from the animal. Despite your precautions, you might accidentally come dangerously close to a croc or gator. Fortunately, crocodilians rely on the element of surprise to capture prey, so it's extremely unusual for one of these animals to pursue a person on land. Crocodiles and alligators, however, are not as sluggish on land as some people believe, though they're not as fast as many other people think, either. The land speed record for a crocodilian is about 10 miles per hour (about 17 kilometers per hour) and these animals quickly grow tired when running on land, which means that as long as you can see it coming, any teen or adult in decent shape can easily outrun one of these animals. Run away from the water, as crocodiles and alligators seldom run on land unless they're trying to get back into the water and out of danger. The commonly-repeated instruction to run in zig-zags is useless: the quickest way to put distance between the animal and you is to run away in a straight line. 6. Fight back if you're attacked. Crocodilians frequently deliver a single, quick defensive bite and then immediately let go. If this occurs, just try to get away from the animal as quickly as possible. In predatory attacks, however, as well as in some defensive attacks, the animal doesn't let go and will often try to drag a person into the water or underwater. Crocodilians can stay underwater for much longer than humans can, so the only hope of survival if you're attacked in this manner is to fight back and get away. Simply struggling and trying to pull free is usually futile and may induce the animal to go into an underwater death roll, during which an arm or leg stuck in the crocodile's mouth will likely be ripped off. A purposeful, deliberate attack on the animal is therefore a better option. - Go for the eyes [...] - Go for the nostrils or ears [...] - Go for the palatal valve" "A tree or a place where the crocodile or alligator can't reach you may serve as temporary shelter, but if you cannot escape until the animal is gone, it isn't very safe. Crocodilians are capable of slowing down their metabolism so they can guard a tree for weeks at a time without food breaks." Source and further information: http://www.wikihow.com/Survive-an-Encounter-with-Crocodile-or-Alligator