It's a tragedy that visitors from Nebraska to an artificially-created environment like a Disney Park might never anticipate, regardless of signs, and especially in less than a foot of water. Often people chide visitors to Yellowstone for throwing common sense out the window as if the NP were Disney World. But even Disney World can't control nature.
Gators are a local species throughout the South. When we lived on the NC coast near Emerald Isle, it was common to spot them, and there were news reports of dogs being snatched by gators. Friends with a pond in their back yard by a marsh in SC discover them out there some years.
Now we live in Florida. A neighbor (with a video to prove it) heard a thump at the front door of her home three weeks ago, opened it (expecting a UPS delivery) and found a 4-5 foot gator there.