+1 for the z-bolt. It is really amazingly bright, day or night.
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I used a pair of these last year to measure goliath grouper underwater. The green is so much more effective vs the red. As we divers should know, water filters red light, so red is a very poor choice for underwater laser apps. These z-bolts are just Ok. It would better if I could easily turn them on just momentarily to reduce risk of hitting an eye, so I'm working on something custom for that this year. High power laser diodes are cheap. Anyway, here is some video of the lasers I first used (z-bolt):
Using lasers to effectively measure marine life size
I have a green laser which works very well. Great for pointing out hard to see items on the reef. Some fish will chase the spot on sandy bottoms. You can see the entire light beam on night dives.
And, no, I don't shine it in the eyes of any critters except lion fish.
I have this one.
Underwater Green Laser for Scuba Diving & Marine Use, Waterproof to 200 ft