Would it be a cop-out to blame the brilliance of this invention on science? It certainly plays a role in the genius of this thing. An airtight seal allows you to chug your beer without spilling a drop.
On the end of the stainless steel tube, there's a one-hitter—which you can use to smoke whatever you want. Fill the bottle halfway up and BOOM—water bong.
For a gravity bong, simply light your "herbs" as you're pouring beer out of the bottle. Smoke fills the vacant space and then, naturally, your lungs.