Pooping while orgasming at the same time.
Would you like a brown waterfall?
To aim one's penis just right so at the point of ejaculation the stream of sperm flies overhead, narrowly missing the face in a matrix like fashion. Resembling a waterfall.
"Last night I was masterbating and totally shot a cascading waterfall"
When you make a girl cum at the beach
Guy 1: Yeah, we were at the beach and I gave her a sandy waterfall
A mullet. The "business up front, party in the rear" looks like a waterfall cascading down the poor hillbilly's neck and shoulders
1: Dude, did you see the mullet on that guy?
2: Yeah, that thing was a redneck waterfall.
When you let 4 of your friends cum on your mullet and let it drip on your sleeping friends face.
After a long night at the bar the crew of the excaliber went back to boat and gave the captain a Toledo waterfall
The act of filling up a water truck with elephant semen and having it drive in front and spray the semen all over the road coating everyone and everything in sight. Then having another heavy truck drive behind it splashing all puddles of semen to coat unsuspecting pedestrians and cars alike.
So me and my fellow construction workers loaded up a water truck to perform an elephante waterfall. We are still pending court chargers.
The Act of rubbing sexual organs together while under the shower head
Baby lets go do the "crotch waterfall" thing