I love doing "waterfalls" as you call it, ive always called it buckets or a gravity bong. Another method that requires a bit more work but same idea, is cutting a hole in the very bottom of a Two litre pop bottle, not too big, no bigger then your fingertip. Make a cap/bowl out of whaterver is handy, i use my lung cap which is a pipe bowl shoved threw a pop cap, but any other method such as ermitonto mentioned is sufficient, as long as u can screw the cap on the bottle, fill it with water with your finger or some type of plug on the hole, put on the cap and light the weed as you let go of the hole, as the water exits it fills with smoke, only thing is u have to recycle the water if outside or refill it every toke.