When I see a snake that could be a cottonmouth or copperhead on the Bayou Bartholomew trail, I just turn around and go back. After all, I'm just walking or running for the pleasure of it, so one way is as good as the other. (Yes, there was a day when I was wearing sandals and not paying attention and stepped on a young copperhead who was under some leaves and I was bitten.)
A couple of weeks ago, I encountered a sizable snake that could have been a cottonmouth (also known as a water moccasin) or a nonpoisonous water snake. I didn't want to get close enough to figure out which. I turned around and started walking in the other direction, but remembered I had a disposable camera (recyclable, so they say) in my pocket. So I went back, but not too close, and snapped a not-very-good photo as the snake was crawling slowly off the trail:
I was hoping since I didn't have a zoom lens that I could zoom in digitally on the photo on my computer, but it gets too fuzzy with more zooming than this.
Also, last year sometime I took this photo of a grass snake or garter snake out at the farm below where my treehouse is:
Sure makes me wish I had a good photographer with me at such times as nature presents a good opportunity.