I've fished an old river or oxbow lake in the Black River bottoms for nearly 30 years. It is full of cypress trees, buckbrush, etc., and is as snakey looking as a place could. Over the years I've seen hundreds of water snakes there but only one or two of them were cottonmouths. On the other hand there is a clear water creek in the hills that I've wade fished maybe 20 times and have seen 3 or 4 there. For about about 20 years I spent a lot of time on Greers Ferry and only saw one ever there though I've seen a number of water snakes over those years.