For those who didn't spend a hazy evening of their youth with their head in a 5-gallon bucket, a gravity bong, or "g-bong" uses water and air ... like a 2-liter soda bottle and a socket from ...

One style, which some people refer to as a “waterfall” gravity bong, uses the negative pressure of water falling out of a bottle to pull air through the plant material and fill the chamber ...