Shooting an AK-47 Underwater

Here in the US, we seem to be obsessed with guns, with our right to own them, and with the ridiculous fear that the government is going to try to take them away from us. Predictably, the people who are most vociferous on the issue are not exactly luminaries and scholars with a solid understanding of constitutional law and jurisprudence, which is really putting it mildly and generously...

But since this is a blog dedicated (for the most part) to sharing education and interesting ideas, why don't we take this obsession with guns to watch someone shoot an AK-47 underwater and, most importantly, to learn some fascinating principles of physics to understand what it is that we have just seen?

Explosions and physics... awesome!