Urinating on one's own scrotum, often by accident.
Steve's pants were too tight, and it was very hot out. He had to keep drinking water, so inevitably he wound up having to pee. He entered a McDonald's, and when he got into the bathroom, he realized he also needed to poop. So he sat down on the toilet, and as he let out his stream of urine, he did not yet realize the degree to which sweat had glued his scrotum to his shaft, and received a rock waterfall.
When one urinates through the legs of another person who is defecating.
Pisser: "Bro, I really gotta piss!"
Pooper: "Dude... I'm taking a shit"
Pisser: "Whatever bro, lets muddy waterfall!"
During oral sex you gag so hard you throw up on your partner.
Last night I gave my husband a roaring 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