I have a couple glotoobs... they're OK. I have a red and green; green is definetely brighter. I believe there's also amber and white.
Available with 2 different battery types, with the CR123 being slightly higher price.
Probably would be good, but I don't know if they float. I suppose I could try it and report back later tomorrow. However, the run time isn't all that phenomenal. I put one on the dog collar for night walks, and it probably lasted ... 10-15 hours, maybe. In other words, if you're out of the boat more than 1 night, you might want something else, or at least several of them. Not sure how effective a battery change would be at sea.
Cellphones might work, but the second you get them wet they're pretty useless.
I have the white CR123 - doesn't seem to float, nad supposidly has a VERY long runtime - I think in the 100 hour range (not that I've tried it - the blackout over here on Monday night lasted all of 30 seconds, so..)
Edit:
John, besides a marker lamp, I've already tried this - they actally make an OK "desk lamp" in blackout conditions. I've said before that I'm a ham that works with ARES. Sometimes we get called out for blackouts. Sitting there with the rig on, the glotube gives off more than enough light to take notes on your clipboard, fill out your log (I log EVERY transmisson in those situations - time and what was said - in a BOUND book, just in case) You would be surprized how BRIGHT a little bit of light is in total darkness
NYC's power grid almost failed again these last two days - I REALLY need to spend some cash on a generator, as I have sleep apenia, and I should not sleep without the machine (it does have a 12 volt plug, and a 20 Ah batter would get me through a night, and I havce a LOT more than that around)