I cave dive, so lots of reel/spool work going on. I'd prefer my buddy had a small mask light to illuminate his working with this hands, instead of his bright hand-mounted light jiggling up and down as he winds in or whatever. That quickly moving light catches my eye and makes my heart pound....but it is not an emergency signal, just him winding up his reel. Yeah, yeah, I know, I should be illuminating his reel for him, but in real life it doesn't always work out so well. My point is, there is a time and a place for mask lights, and they don't need to be so strong they blind the buddy. A glowstick doesn't do the job for anything other than gauges....and is not allowed everywhere.