Dive #13 or thereabouts. 80 feet deep off Newport, Oregon. Dive buddy (experienced diver with a speargun) waves bye and 3 minutes later I'm stuck. Removed my BCD, took out the knife, and cut a lot of tangled fishing line off a hook caught on my back. Removed the hook topside. Haven't used the knife for personal safety since, but I dive in a lot better viz these days.