I’ve shot quite a few water moccasins.
The first time I used a .22, nearly point blank range. The guy was swimming right at me, finally stopped about a foot away. (Yes, I was on shore and about to run.)
I fished him out of the lake and counted the holes.
It took seven hits to finally stop the guy.
After that I used a 20 gauge shotgun. Cut the little guys in two, and put a big hole in the big ones. Always shot at the part that was on the surface of the water. Stopped ‘em all.
I put a 7.62x54 just below a water snake and it blew him 20feet out of the water LOL