I can't tell exactly what he is, looks like some form or water snake, Green or Plain Belly but the shot of the head isn't great so I can't be sure. Only critter that would even look like that at all that is venomous is a cotton mouth. Their heads are VERY distinctive. See this. https://www.thesurvivalpodcast.com/5-most-common

I am 95% that is NOT a cottonmouth but won't say that 100% from this image across the interwebs. The pattern on the body is not quite consistent with any of the most likely. Honestly the pattern on the body is more bull/king looking but not aware of any with that dark a pattern in your area.