In a wacky comedy, the water level's rising inside a locked room, and usually, somebody is trapped in there. An unsuspecting person opens the door, and gets the unwelcome surprise of a massive flood pouring out, knocking them right over.
In Real Life, the water would usually just leak out at the crack at the bottom of the door, though it could be blocked up. Often the volume of water is so great that the weight should rip it off the hinges.
Compare Exploding Closet, where there's a pile of solid objects on the other side of the door.
- In one commercial, the young son of a family was filling the tub with water in preparation for a bath but then went away and forgot about it; at the end of the commercial the bathroom door pops open from the water pressure and a wall of water starts to drain out into the rest of the house. The son has a slightly evil grin on his face.
- A variant happens in Episode 6 of Eroge! Sex and Games Make Sexy Games; Kisara wonder why the water suddenly stopped running in an Inn's bathroom, and when she goes over to check, she's blasted by a torrent of cold water gushing out.
- Agent 327: In "Dossier Stemkwadrater", Agent 327 invokes this trope after being taken captive by Dr. Maybe. He convinces Dr. Maybe to give him some time to think about his We Can Rule Together offer, finds a bathroom, locks himself inside and floods the place (even using toothpaste to block the cracks around the door). When Dr. Maybe's right hand man opens the door, the resulting tidal wave carries Agent 327 right back to the lab and takes out all the henchmen there, allowing 327 to get hold of the titular Stemkwadrater.
- At the end of one Garfield story, after Jon, Odie, and Garfield return home from a trip, they're victim to this when Jon opens the front door to their house, because Garfield left the tap on (he didn't want his own sponge collection to dry out).
- From Cats Don't Dance, after giving a press conference on his upcoming film, studio honcho Mammoth opens the door to the sound stage, unaware that the Funny Animal performers are undergoing a deluge as part of The Villain's effort to sabotage their careers. Since this is a cartoon, the water ignores the laws of fluid dynamics, flowing instead according to the Rule of Funny. Mister Mammoth was most displeased.
- This happens at the end of the zany things Paddington does in the bathroom.
- In the Laurel and Hardy short Brats, Ollie Jr. fills up a bathtub, gets knocked into it, and accidentally strains on the shower head when he gets out. Later, Ollie prepares to enter the bathroom to get Stan Jr. a drink of water, only to be knocked down by the flood.
- The 1975 detective drama The Drowning Pool has gumshoe Lew Harper and his old flame Mavis be imprisoned by The Villain in the hydrotherapy room of an abandoned mental hospital. They try to escape through the skylight by flooding the room, but the material won't break. There are only moments of air left, and no way to drain the water due to the pressure. Just then, The Villain and The Dragon arrive to dispose of the snoops, and they open the access door. Surprise!
- In Jumanji, the abandoned house floods from rain due to the titular board game's effects. The police kicks the door open only to be greeted by a wave of water.
- In The Return of the Pink Panther, there's a scene where Inspector Clouseau is bathing while using a hand shower sprayer. The phone rings, and he finds he can't shut the sprayer off, so he places it in the toilet while he goes to answer the phone. He shuts the bathroom door behind him, and we can already see the toilet starting to overflow. One lengthy phone conversation later, Clouseau returns to open the door to the bathroom. *SPLOOOOSSSHH!*
- A non-comedic example happens in Titanic (1997), when an Slovak immigrant and his child, neither of who know a word in English, get lost in a flooding hall as the ship sinks. He walks straight to a locked door, which promptly bursts open and floods the hall completely, sweeping them away.
- A variation of this happens in Beanotown Battle: Book 2 of The Diary of Dennis The Menace: Dennis, instead of trying to photocopy 10 pages of detention writing in the Secretary's Office, somehow manages to accidentally photocopy 10,000 pages. When the Secretary herself opens the door, she is buried by an avalanche of pages (with Dennis surfing on the tide, described as looking very proud of himself). Mrs. Creecher says that it took all afternoon to dig her out.
- In the Star Trek novel The Final Reflection, an Actual Pacifist character sets up a trap for an assassin by turning on the hot water taps in his bathroom, closing the door, and hiding under the bed.
- Happens in Schlock Mercenary when the Toughs are salvaging the Touch-And-Go, which used to belong to an amphibious species and lost its artificial gravity several times during the salvage operation.
Tagon: I want these quarters to look as nice every day as they do today. [opens the bunkroom door; cue the tidal wave) ...Nicer, even.
- The Magic School Bus: In "Wet All Over" the girls' bathroom is flooded due to a faulty faucet. Guess what happens when Tiffany opens the door?
- Spongebob Squarepants:
- In an episode, SpongeBob cries so much he fills up his entire house with tears. Squidward opens the front door, and gets knocked right over.
- In another, Pearl runs to the Krusty Krab crying to her dad over being dumped by her boyfriend. SpongeBob gets blown back by her tears flooding Mr. Krabs' office and busting the door open.
- The Popeye short "Happy Birthdaze" has this happen to Popeye when Shorty floods the bathroom. Twice.
- House of Mouse: In the short "Daisy Bothers Minnie", Daisy stays over at Minnie's house and starts a bath in her tub, and soon forgets about it while leaving the water running. Later, when the two are cornered by an escaped lion, the bathroom door finally gives way and floods the house, and also washes the lion back to the zoo.
- In one of the early The Simpsons shorts, Bart decides to get immersed in his bathtime playing and forgets to turn off the taps as he submerges himself and pretends he is Jacques Cousteau. He jokingly shouts for help, which Homer takes as a genuine cry for distress, causing him to open the door and be splashed.
- On the Toy Story short "Partysaurus Rex", Rex helps Bonnie's bath toys by turning on the faucet so they can party. All goes well until Rex realizes that the bathtub is going to overflow. His attempts to turn off the faucet fail, and when the other toys come looking for him, they are met with a wall of sudsy water.
- The Amazing World of Gumball: In "The Responsible", Anais accidentally floods the whole house by leaving the bathtub faucet running. And after Gumball and Darwin rescue her and escape through the chimney, an angry Nicole comes home from a parent-teacher-conference and opens the front door only to be greeted by water suddenly blasting out.
- In 6teen's "Silent Butt Deadly", Nikki ends up flooding Jonesy's bathroom (long story), and when he finally opens the door, he's knocked over by a wave of dirty water.
- Dastardly and Muttley in Their Flying Machines: At the end of one "Magnificent Muttley" short, when the rest of the Vulture Squadron returns home, unbeknownst to them, Muttley had left the faucet on. Cue them (minus Muttley) being swept away by the tidal wave.