It's actually pretty simple, you light the slide piece holdingwhatever it is you are smoking, it goes down a tube on the bong andgoes underwater, the sucking motion is pulling air through theslide and down the tube. The air at the bottom of the water istrapped, and the only place it has to go is up through the bong andinto your mouth, this is why a bong bubbles, I hope I explainedthis well enough.