When Haley first goes to her father's condo, she's out in the rain, yet when she gets inside, she's not wet at all.
Shortly after Haley finds her Dad in the crawl space under his house, the amount of dirt on her father's face changes from shot to shot.
When Haley is just beside the drain pipe, an alligator nearly tears her arm off. But later in the film, after escaping from the basement, she barely has a scratch where there should have been a gaping wound.
Helicopters cannot fly in hurricane 5 level winds.
There was no need for the policeman to exit the boat. Outboard engines can be tilted to lift the propeller out of the water for the express purpose of defouling it.
When Haley's father tells her to swim to the boat, he tells her that she can "Swim faster" than the many Alligators in the water nearby. However this would be highly unlikely as the average adult Alligator swims at speeds up to 20 mph, While 23 time Olympic Gold Medalist Michael Phelps topped out at about 6 mph.
Alligators don't hunt communally. They also don't build underground nests because they need sunlight to keep the eggs warm. And female alligators try to seek secluded areas away from humans and other alligators to build their nests.
All vehicles display a front license plate, a dead giveaway this is not set in Florida, since only rear plates are provided there.
When Haley and her father are outside after escaping the crawl space, Haley's hair isn't blown by the wind - even though it's a category 5 hurricane that is almost toppling trees.
The crawlspace is ringed by a series of decorative lattice made by brick appearing weakly held. Any series of sharp bangs could easily make hole(s) large enough for the two to escape to the outside. There was a toolbox, pipes, etc. for available implements.