haha thats my bong! Thats thats actually a double perc.. ;-)

It pulls the smoke through the water, then out, then down into the water again, then out small diffuser holes, then through more water, and finnaly into the air (unless its a multi-perc, in which case rinse and repeat). It makes for a really smooth smoke. It does require a good set of lungs to get it up there, but it is really worth it.