Hey-

Ermitonto, I think what you are talking about is a gravity bong, or a bucket.

A waterfall is this-

You put water in a 2 Liter soda bottle (pretty much fill it up) and then put some herb in a tin foil bowl (like you said earlier) and screw it onto the bottle. Then, without trying to make too much of a mess, you poke holes into the soda bottle, causing the water to gush out of the holes, like a waterfall (kinda) The rushing water will cause the smoke to fill in the bottle. When all the water has drained, unscrew the bowl and inhale.

I might be wrong about this, but this is what I always knew to be a waterfall.