If you're into lasers, you should already be following Smarter Every Day. He's got a ton of incredibly cool and educational videos and his latest is no exception. Destin does a great job of explaining internal reflection and it's relationship with angle of incidence. This same relationship with the laser and the water he shows in this video happens with the dichroic filters in your laser projector too. If the beam doesn't hit the filter at close to a 45 degree angle, the efficiency of the mirror drops dramatically.
PS. Don't shoot a laser pointer into the air like this. We're assuming he filed the appropriate FAA paperwork.