Is it just when you touch the water dish, or also when you spot clean the enclosure/touch other things? My young scrub is very cage defensive, unlike every other snake I've ever handled. He doesn't like you to touch any of his stuff and can only be picked up sans-hook if you sneak attack him while he's sleeping in his hide! Out of the enclosure, he's a totally different beast. But for some reason, once he crosses the threshold into his lair...watch those fingers!