Quote Originally Posted by Professor Dan K.
its like a portable gravity, same concept used but theres a hole in the bottom of say a sobe bottle, bowl on the cap, water in the bottle. light the bowl let your finger off the hole, water runs out sucks smoke in (gravity) unscrew lid get ripped

:greenthumb:

theyre amazing by the way, kind impractical but get you fucked up

Not Gravity, but rather a vacuum created by the water draining out. And that vacuum wants to get filled up with whatever it can, that being the smoke :rastasmoke: