Gators are are almost always friendly ... perfectly willing to invite you to lunch and eat off your hand.
All the way to the shoulder.
Gators are ambush predators that lie in wait, typically near shore, waiting for small animals to come near the waters edge for a drink. They often lay on the bottom near shore or float so just the eyes and tip of the snout are visible. Add a few water plants and their natural subdued coloration and they can be hard to spot.
Joggers who run along the waters edge and step on them and dogs walked near the water are common victims.
I know a man who was caring for a water garden feature with water lilies when a hidden alligator grabbed his wrist. Over the next few minutes, while the man fought to keep from being dragged under water, the gator rolled, disjointed his elbow and ripped his forearm off. Had his arm not separated he would likely have been killed outright by drowning. As it was the man made a good show of it by holding his own against a powerful animal, and maintaining enough presence of mind, despite the physical and mental shock, to control the bleeding by wrapping a belt tightly around the stump.
On the positive side he has a pretty good sense of humor about it and has played Captain Hook several times in the community theater productions of Peter Pan. Ironically he doesn't blame the gator and expressed regret that the state demanded that the animal die.