How do lasers perform in water?

Hello, I do not know much about lasers, but do these high power laser work under water? I mean completely submerged? Also how do they work if they are out of water but say you want to pop a ballon or something that is under water...Does the water effect the power of the beam? And if so does it have a posotive or negative effect?

I love watching the demo vids on these high power lasers and I just saw the one with the water ballon, I was thinking what if the balloon was waited and filled with air then placed inside of water...I wanted to know if that would still work?

the OC lens is tuned for air interface, so the divergence will be poorer under water (unless the lens is plano-convex, but I haven't seen one that is). Also, the water will act as a heat sink for any objects contacting it, so baloon popping ability will be dramatically decreased under water. It's likely that he was aming at an air pocket in the waterbaloon popping video, which would eleminate this heatsinking effect.

Ok great, thats exacty what information I was lookign for, thank you!

If you shine the laser from the atmosphere into the water, refraction becomes an issue. Some of the light will be reflected off the surface, which will of course decrease the power. How much depends on the incidence angle, at some point, no laser will reach the balloon, no matter how powerfull the laser is. And, that reflected light becomes a safety risk too.

Also, the distance to the object is a factor, as water usually has impurities which will scatter light, making the spot more diffuse and less defined.

And remember, most lasers are not water tight (wicked's spiders are, as far as I know)