Looking at the picture, the first snake I identified as a cotton mouth was the brownish(lighter colored) one as most I've killed were that color. Have seen a few darker ones too.
We get them from that color to coal black around here. I agree with the 12 ga. #7 1/2 approach to snake repellant, I can't see how you can throw those little granule thingies hard enough to properly repel a water moccasin. Anything that doesn't immediately identify itself as non-poisonous gets the 12 ga. treatment from me, I apologize to them afterwards if I mistakenly kill a harmless one. I've got cats to deal with the rats.
