I had a fair amount of experience with water moccasins in FL in the 70's.
I found them to be very curious, and not the least bit tumid. I would be cutting line for a transit sight and see a cottonmouth paralleling me at a distance of just a few feet. Thirty yards later he would still be there matching my pace. I finally understood that I was only there to scare up his dinner. While this wasn't a daily occurrence it happened more than once. The only time that I really felt worried was when I was in the water with them and they would dive below the surface. It tends to make your heart race a bit. I didn't have kids or pets to worry about, so shooting at them wasn't really on my mind. The most vicious snakes that we had were the southern black snakes, mean, foul tempered, and a nasty bite...and fast!