I don`t think that one will hurt him.
X2 That is a water snake. It is not venomous.
A man I know had a fearless Jack Russell that survived several copperhead bites. He'd get bitten and still be able to kill them. His owner nicknamed him "Zipper Head". His first encounter with a canebrake was his last encounter with anything. I don't recall if he killed the snake but that wasn't the problem.