Z-City Municipal Pool. District 4.
Temperature: 38°C (100°F). Humidity: 90%.
The sun beats down on the blue water. The pool smells of chlorine, sunscreen, and the faint metallic tang of god-sweat.
Since the Merger, the public pool has changed.
The "Kiddie Section" feeds into a waterfall sourced from the tears of Nymphs. The "Lap Lane" is actually a slice of the River Styx (it's good for cardio because if you stop swimming, you age rapidly).
On the high lifeguard chair sits a figure of absolute authority.
Blonde hair, perfectly coiffed despite the humidity. Teal whistle hanging from a neck that has never known strain. He holds a trident made of plastic (city regulation), but in his hands, it radiates the aura of a planetary devastation weapon.
Poseidon. The God of Gods. The Lifeguard of Lifeguards.
He stares at the water.
He does not blink.
To blink is to miss imperfection.
Tweeeeeet.
The whistle cuts through the noise of screaming children like a blade.
Poseidon points the plastic trident at a teenager running on the deck.
"You," Poseidon speaks. His voice is quiet, cold, and reaches every corner of the facility. "Bipedal motion exceeding 4 km/h is strictly prohibited. Your gait is sloppy. Your balance is offensive."
"Uh, sorry?" the kid stammers.
"Do not apologize. Correct your existence. Walk."
The kid walks. He walks like his life depends on it. Because it does.
The Shallow End.
Saitama floats on his back.
He wears red swim trunks with a yellow stripe. He holds a pink pool noodle across his chest.
He drifts aimlessly, staring at the square-ish clouds left over from the Glitch incident.
"Genos," Saitama murmurs. "The water is warm. Too warm. Is someone peeing?"
Genos stands at the edge of the pool. He is not swimming. He is wearing a custom-made waterproof chassis with "LIFEGUARD ASSISTANT" stenciled on the chest.
"Negative, Master. The water temperature is elevated due to the proximity of the Fire Giants' communal jacuzzi in the next district. I have filtered the urine content to 0.00%."
"That's..." Saitama drifts into the lane rope. "...a weirdly specific percentage. Thanks, I guess."
Saitama spins upright. He splashes a little water on his bald head.
"Hey, Ocean-Guy! Can you turn down the heat? I feel like a boiled egg."
Poseidon looks down from his tower.
He sees the bald anomaly. The only being in existence who dares to address him without trembling.
Poseidon sighs. It is a graceful, divine sigh.
"The temperature is optimal for muscle relaxation," Poseidon states. "If you cannot withstand it, retreat to the spray-ground. It is designed for... weaker constitutions."
"Spray-grounds are for babies," Saitama splashes water at the tower.
The water stops mid-air.
Poseidon glares. "Do not splash the Lifeguard."
The Disturbance.
Gurgle.
The drains at the bottom of the deep end (12 feet) begin to bubble.
Black sludge leaks from the grates.
The water turns murky green. The smell of chlorine intensifies until it burns the nostrils. It smells like a chemistry lab exploding inside a dumpster.
"DIRTY..."
A voice gurgles from the filters.
The water erupts.
Screams echo. Swimmers scramble for the ladders.
A monstrosity rises from the deep end.
It is made of slime, band-aids, lost hair-ties, and chemical residue. It has three heads shaped like drain clogs.
The Chlorhydra. (Threat Level: Demon).
Born from the chemical reaction between mortal filth and divine runoff.
"I AM THE SCUM OF THE POOL!" The monster roars, spitting acid. "NO RUNNING! ONLY DYING!"
It grabs a swimmer—Pri-Pri Prisoner, who was practicing his butterfly stroke.
"Angel Swim!" Pri-Pri yells, trying to flex out of the slime. "It's so sticky!"
The Tyrant Reacts.
Poseidon stands up.
The plastic trident in his hand melts, unable to contain his grip strength. He discards it.
He summons the real trident—magically concealed in his whistle.
"Filth," Poseidon whispers.
The God of the Sea steps off the tower.
He doesn't fall. He walks down invisible stairs of pressurized air.
"You dare," Poseidon says, his eyes glowing with terrifying malice. "You dare pollute my perimeter?"
The Chlorhydra lashes out with a tentacle made of wet hair.
Poseidon doesn't dodge. He creates a zone of absolute rejection.
Divine Move: Hydro-Barrier.
The pool water rises up, separating clean water from the monster's slime.
"Be excised," Poseidon commands.
He thrusts.
Air bullets pierce the monster's slime body.
Thwip-thwip-thwip.
Holes open in the monster. But being liquid, it regenerates.
"CLEANLINESS IS A LIE!" The Chlorhydra sprays a jet of pressurized toxic sludge at Poseidon.
Poseidon's eyes widen.
To be touched by that... refuses.
He moves faster than light. He dodges.
But in dodging, he leaves the splash zone open.
The sludge flies past him.
It hits Saitama.
Splat.
Saitama stands in the shallow end.
Green slime drips from his bald head. A used band-aid is stuck to his cheek.
The pink pool noodle sizzles as the acid eats it.
Silence falls over the pool.
Even the monster pauses.
Genos's sensors flash red. [CRITICAL MOOD SHIFT DETECTED.]
Saitama wipes the slime off his eye.
He looks at the band-aid on his finger.
"I just..." Saitama whispers. "I just showered."
He looks at the monster.
The "Serious" shadow covers his face. The art style shifts from summer-fun to detailed anatomical horror.
"You made the water gross."
Saitama tosses the melted noodle aside.
He wades forward.
The water offers no resistance. He moves through it like a torpedo.
"WHO ARE YOU?" The Chlorhydra screeches. "ANOTHER GOD?"
"I'm a guy trying to relax," Saitama growls.
Poseidon steps back. He knows what is coming. He creates a water shield around himself to protect his uniform.
Saitama reaches the deep end.
He climbs onto the diving board.
The fiberglass board groans.
"Cannonball," Saitama says.
Serious Series: Serious Cannonball.
He jumps.
He tucks his knees to his chest.
He curls into a perfect sphere.
He hits the water.
KAAA-DOOOOM.
It is not a splash.
It is a hydraulic displacement event.
The impact forces the water molecules to flee at hypersonic speeds.
The entire volume of water in the pool—500,000 gallons—is ejected instantly.
Along with the monster.
The monster is vaporized by the sheer water pressure. The hair, the slime, the band-aids—atomized into mist.
The water shoots straight up into a pillar three miles high.
The pool is empty. Dry concrete.
Saitama sits in the center of the dry pool drain.
"Checkmate," he says.
The water comes down.
It rains over the entire district. But the monster is gone. The contaminants were destroyed by the friction of the splash.
The water refills the pool.
It takes ten seconds.
Saitama floats to the surface of the now-pristine water.
"Ah," he sighs. "Clean."
The Aftermath.
Poseidon stands on the pool deck. He is dry. Perfect.
He looks at the pool.
The chemicals are balanced. The filth is gone.
He looks at Saitama drifting on his back again.
Poseidon lifts his whistle.
Tweeeet.
"You," Poseidon points at Saitama.
Saitama looks up. "What now?"
"Excessive splashing," Poseidon declares. "And destruction of city property (the diving board is gone). You are banned for 15 minutes."
Saitama groans.
"Fifteen minutes? Fine."
He climbs out of the pool.
"Genos, get the snacks. Let's eat while we wait."
"Yes, Master. I have waterproofed the sandwiches."
Poseidon sits back on his tower.
He watches the water ripple.
He adjusts his sunglasses.
A tiny, almost imperceptible smirk crosses his lips.
"Technique was... adequate," the God of the Sea mutters. "For a monkey."
OVA END.