An aunt of mine, before I was born, got bitten by a cottonmouth down in Chambers Creek in Ellis County, near Italy. They could not siphon all of the poison out, this was in the 40's, and the residue contaminated her bloodstream, and the venom destroyed, slowly, the marrow in her bones. Took her several years to die, a horrible death. In today's world, it probably would have been serious but not fatal. Still, a cottonmouth is not a snake to be taken lightly. That is a decent sized cm, but they do get a bit bigger than that one.