I know that these "deflators" or "fizzing needles" are used offshore, but from how deep will fish need to be treated to prevent problems? I would think anything below 40 ft or so would, but please educate me on this. Also, are these needles for equalizing pressure between the air bladder and the surface, or is it like the benze that humans have to watch for (separation of nitrogen or oxygen in the bloodstream)? Thanks