Northern water snakes are aggressive compared to many. They are not at all afraid to strike, and it hurts like heck. Your hand will not swell up and fall off, but you'll wish you hadn't stuck it in his face if bitten.
Good chance this isn't a water snake, even after looking at it on my laptop I can't say for sure. Regardless, I'd either cut his head off or simply move on. Don't prick with "harmless" snakes unless you're into pain.