Living in Florida, the list is quite extensive. Even if I exclude Sharks, Jellyfish, and other marine threats since I live inland and rarely go out to the beach.
Large Animals: Alligators, Florida Black Bears and Panthers, and Wild Boars which are very ill tempered.
Snakes that are a danger to people due to venom: Copperheads, Cottonmouths (water moccasins), Coral snakes, Eastern Diamondback, Timber and Susky Pigmy rattlesnakes.
Large Snakes: Burmese Pythons, thanks to the dumbasses that either released them or allowed them to escape. They are such a problem that there are now hunting seasons for them.
Smaller but dangerous threats: Fire Ants, Trap-Jaw Ants, Brown Recluse Spiders(do not look for wound images, trust me) Black Widow Spiders, Toxic Caterpillars, small scorpions and other assorted spiders.
And of course, potentially deadly bacteria and amoebas in water. That amoeba is very rare, but typically lethal as it eats your brain. If the gators and aquatic snakes aren't enough incentive, just stick to pools and water parks and thank me later.
Since people are animals too:
Where I live, Central Florida, is not only racially diverse with the permanent residents but also a tourist hotspot - imagine driving on heavy traffic roads with scores of people from all places of the world with different driving laws and customs.. And most of them have no idea where they are going. Very frustrating at times, dangerous at others. People that are looking for signs or focusing too much on their GPS can be dangerous, so be aware of what people around you are doing and learn how to spot rental cars.
And, perhaps worst of all: Florida Man/Woman. Just google Florida Man and Florida Woman news stories.
This is a little off topic.. But important.
If you visit and choose to swim in the ocean, PLEASE learn about Rip Currents before you set foot in the water. And, especially you Brits and people from other fair climates.. Wear lots of sunscreen. I've seen more lobster red Brits than you would believe.