I'm not a physicist as well but here's my thought:
Laser and energy guns don't exist in real life (or at least not used in the current world market yet) so lets keep that out of the discussion. Bullets, however, do exist of course so lets use bullets as the main argument here. Mythbusters have tested how far bullets travel when they enter water and see if someone can survive if they jump into water and use water as a bullet-proof substance. Long story short, the result was that bullets can't travel far into water AT ALL. They tested with a 50 cal. bullet and it only travelled a mere 14 inches into the water before breaking into tiny shards uncapable of harming someone.
You can check out the whole video here:
https://www.youtube.com/watch?v=v1uaLWAZXfk(50 cal. test starts at 15:10)
I also have to say, how can a bullet travel into water and exit water at the same time? This doesn't happen in real life. In reality, you can't have floating water, thus making a bullet travel in water and exiting water impossible UNLESS you shoot the gun underwater while aiming at the sky. Then we have this problem of having to be less than 14 inches below the water while shooting the gun and blah blah blah.
In conclusion, PB2 physics ≠ reality physics.