Growing up in Florida, we would swim, tube & ski all the murky waters of rivers like the St. Johns. I can remember seeing them around every corner and on every bank..even while you're sitting in the water 20' away putting on your skis.
Never had a problem.
Later, as a stupid teen, we'd do things like chase & grab them while canoeing.
(which, by the way, I think is a crime. No molesting the gators/manatees.)
Like any wild animal, if you're bigger than they are - their first instinct is to get away.
But just like the "tame" nurse shark, if you corner it or step on it, you may get a surprise.
I wouldn't worry about it. Snorkeling, or diving, I've seen them underwater or on the bank sunning themselves at Blue Springs and Silver Springs. They've never had any interest in us. If I'm in the water, I've kept a healthy distance from the big ones, but the ones smaller than you are no more threat than encountering a strange dog on the street. You might lose some blood if you provoke it, but in the end you can just lift it out of the water and bash it if you had to convince it to let go.
I think the statistic is that every single body of water here in Florida has about one gator per square acre. Heck, we've got a half-acre retention pond behind our homes in this subdivision and there's a curious little 4 footer in it. Any time you walk along the shore of the pond - he comes close and follows you around. Probably getting fed by some idiot.
When you're down here next time, I'll take you over to Lake Jessup. lol.
It has the largest ratio of gators in America.
You go out on the water at night in a small boat and sit in the dark with a flashlight and you can count hundreds of pairs of eyes staring back at you.