I live in Southern Missouri, and think I saw my first Cottonmouth yesterday.

It was in a stretch of trail in front of my horse and me that was under water. It swam for about 20' through the channel in front of us, then came out on land and went down into the main stream below. I know that they are considered aggressive, but also have read studies where 50% will flee rather than attack, if given a clear option.

It swam with body partially above the surface, was a solid dark color, no pattern.

What I think may be a final diagnostic was the way it moved out of water. It moved on ground with a VERY definite sidewinder pattern, not the forward I see in snakes on ground around here. I've never seen a snake move like that on the ground here.

I can't find a THING about ground movement for either water snake we have here (the other being the Northern Water Snake, non-venomous), so I'm curious if anybody might have observed this movement pattern commonly in either species.

Thank you.

What county are you in, in Missouri? Plainbelly Water Snakes in Missouri and very large Northern Water Snakes (most smaller ones have a distinct pattern which you are probably familiar with) can also be solid colored. And terrestrial snakes will also swin some time.

Its a good description but from the description it is hard to say one way or the other.