waterfalls involve water falling down a fall, ie like the water coming out of the bottom of a bottle, flowing into the sink.

gravity bong like you made, works on the basics of gravity....but whatever your obviously a ameture to smoking, but heres a tip, put that bottle with the bowl to the bottom of water, slowly pull up while lighting (make sure u have a good bowl or if your using tinfoil like i think you did, make sure theres a good flow of holes and dont pack to bowl tight), when you have a HUGE cloud of smoke, un screw the bowl, push down the bottle while inhaling..bam! by the way NEVER NEVER let the bottle/bowl come out of the water before the hit, as lots of smoke escapes. if you do it right, prepare to get baked

peace