To start out with, by the time the Seminoles started settling Florida, they already had guns. So lets turn the clock back a bit more. For thousands of years, alligators were on the menu for people living in Florida. They weren't really a common meal, of course, but their bones do show in trash middens alongside other game animals and fish. At the time of contact with the Old World, northeastern Florida and southeastern Georgia were Timucua territory. The Timucua sought out European alliances during war between the three Timucuan alliances that dominated the area. The French allied with the Saturiwa, which allowed Jacques le Moyne the opportunity to capture various aspect of Timucuan life in his art. This included an image of the Timucua preparing for a feast. As you can see, a young alligator is already cooking over the fire and another is about to be put on the rack. But those are small alligators, what about the adults? Luckily, le Moyne has an answer for that too.

In this illustration, a Timucua hunting party gets an exaggeratedly large alligator to bite down on a pole (foreground), then uses the pole for leverage to flip the alligator on its back. Once it's turned over, they're able shot its softer underbelly with their bows (background).

Not necessarily historic, but hopefully on topic. Alligators are not particularly aggressive and rarely attack people. There were about a dozen alligator attacks in the last decade. Considering the millions of people who have contact with the creatures, this number is remarkably low. If you don't feed the reptiles or swim at dusk or in the dark, or bother them during mating season when the males are especially aggressive, alligators for the most part will leave you alone. I have been up to my armpits in Florida swamp many times in close proximity to gators and still have all my extremities.

Secondly, much of the Everglades where the Seminoles live is quite shallow. In most places it is inches deep. Gators will dig holes and trench through, but it is not like the water in most places is deep enough the dangerous animals can swim up upon you undetected.