1. Fast forward the movie to the part where the skinny little guy has to dive under the water inside the sub to turn the valves. His buddy gives him a tube that blows out air so he can breathe underwater.
2. He dives down, and gives up, returning to the surface.
3. The dude in charge tells him to get back down there, so he does.
4. After a little trying, a huge pipe falls on his back, so he cannot move as freely as before.
5. After trying for a while to reach the last valve, he decides he needs more air, and reaches back for the tube.
6. The tube, which was constantly blowing out air, for some reason, is not blowing air bubbles out, nor is it moving in the water. If air was coming out, it would sway the hose back and forth, and air bubbles would emerge. For some odd reason, neither happens.