Like someone else said, just being near the water's edge is just as dangerous if not more than swimming. They ambush animals that come to drink, that's their thing. And trust me, once a gator grabs your dog you aren't going to be able to do anything about it, just look at that poor kid at disney land. You know that dad did every superhuman feat imaginable and he couldn't save his kid.
During mating season when they are on the move, they will be in any body of water, even a puddle, and there can be a very big gator taking a rest in a very small body of water where you wouldn't expect them to be able to be invisible, but they are
they have no qualms about taking dogs with people right there, I read accounts every year of leashed dogs being taken at the water's edge.