I was really eager to try a gasmask & rebreather bag underwater but things didn't go as planed. Because of the water pressure, it's nearly impossible to breathe just a few feet under the surface. That's actually why scuba was invented... you can't just take a hose or air supply and bring it with you, unfortunately.

Long story short, I had to stay near the surface in order to breathe with the bag. Didn't stop me from capturing some sexy footage of the experiment...