I was in N.O. doing a bit of Search and Rescue in my boat. In many of the areas I went through the water was up to the eaves of the houses, so you could forget wading. Treading water maybe, but you don't last long in that stuff. The paint is now peeling off my boat motor which previously was almost flawless. You don't want to see what it does to people that have been in it for a while. That is probably one of the most horrible things I have seen.
Your moccasin doesn't look that big to me, but then I pretty much grew up out in the marsh. I've seen many bigger. It always sucks when you don't know they are there until you feel them sliding across your foot or smell them

Chicken snakes, King snakes, and Hognose snakes can live, but Moccasins got' ta go because you don't want to run into them in the dark.
-Muddy