The coral atoll of Rhodoreef contained within its borders a veritable hotpot of variety—from the glittering monoliths of downtown Calliathron to the mobile homes of the working classes. Dea's train of thought took yet another turn as she sped along a highway, seated at the back of a state vehicle.

That was when she caught sight of herself on street graffiti.

Messy brushstrokes of color depicted her face on a large wall in the distance. Abstract waves radiated out in turbulent swirls, touched with the hues of twilight. Emblazoned in gold were the words "Queen of Waves". Underneath the artwork, the tagline read "Child of Calliathron, Bane of Humans."

The otherworldly experience reinforced the sensation that she was living a simulation rather than reality.

She averted her eyes and focused on the Tower of Calliathron, popping out like a beacon against darkening waters. The city center was not located at the very heart of the lagoon. The tip of the former seamount jostled it aside as it rose up and peeked above the water. This central island bloomed with coconut palms—a natural spire to mark the grandeur of the metropolis. On the western side of the island was the administrative district of Calliathron. It was a grid of orderly buildings, which included the sprawling military base of Fort Sol Dadva.

This was her destination that evening.

The submersible exited the highway and followed the curving road line down to seafloor level. Algae swayed on the wayside while waning sunbeams bled orange into the teal waters and mottled the mounds of concrete.

"Has everyone arrived?" Dea asked, the words plopping out in the quiet interior. "Am I the last?"

"His Excellency is also on the way, Your Highness," the driver replied.

"I see."

Soon afterwards, they turned to a deserted roadway. It led to an oblong splotch on the map that marked Fort Sol Dadva. As dusk gradually approached, the choir of fish swelled above the vehicle's drone.

The melancholy of the moment appealed to her. The past few days were a frenzy of activity. Dea's popularity had skyrocketed as the televised speech blew over Calliathron like a cyclone. Excerpts were all the rage on social media, and her face had turned into a meme. She was hounded by the press while the city-state reeled from the bombshell she had dropped.

It was incredible how fast the tide turned in favor of this new policy, strengthening the incumbent government. The Opposition was in shambles, and there was hardly any resistance from the Youth Council. In fact, the military reserve was called to arms and the youth were being enlisted in the army.

They breezed past security checkpoints and entered the compound. A slate-grey wall marked the perimeter, curving inward like the outer half of a torus. Surveillance drones hovered above—red sparks winking against the gloom.

"We're here," the driver announced.

The submersible drew to a stop at a facade of metallic wall cladding. The midnight blue flag of Calliathron, mounted on a pole, waved in the current.

A young merman in uniform swam up to open the door. "Your Highness."

"Thank you." Dea drew one last lungful from the oxy-hose and slid out.

The merman escorted her into the airlock.

Once inside, the picture of minimalism greeted her. The hallways emanated a dull, metallic sheen under strips of LEDs, matching the brutalist architecture on the exterior.

An elevator ride later, Dea approached an unassuming door. Before the man could open it for her, she gave it a mechanical knock and entered.

It was a large, windowless room that took on the appearance of both a conference space and submarine bridge. Neon strips lit up the concrete and dark metal. Seated around the cylindrical island at the center were several merpeople—including Talmus Mora, the supreme commander of the campaign against Serendiva.

"Good evening, Your Highness," Mora rumbled, ensconced in a high-backed office chair. "Ladies and gentleman, let's welcome Queen Dea."

Heads bowed.

Dea greeted them and propelled forward with one powerful tail thrust. The dead silence hinted at the heavy foam that lined the walls.

"While we wait for Hal, I think a few introductions are in order," Mora said while she slid into an empty seat. "On your left is Prof. Ravul Soma, Calliathron's most esteemed physicist—as you may already know. He had helped pioneer our weapons systems, especially the particle beam cannons."

Dea's eyebrows rose as she turned to the bearded merman next to her. "Glad to make your acquaintance, Professor."

"Likewise, Your Highness," he said quietly.

"Please call me Dea. I've seen your talks on Surfeo." A memory surfaced in Dea's head like a window into a different lifetime.

The man nodded, a spark igniting in his eyes at the mention of his work.

"And next to Prof. Soma is our chief biochemist, Prof. Golub Sevaler," Mora continued. "It's thanks to him that we have our revolutionary new treatment for malignant tumors. And even the new GM bioluminescent plants."

He was an old, smallish merman with veiny hands. There was something greasy about him—from his gel-slick hair to his watery eyes. Dea couldn't help musing on the scientific breakthroughs that had brought him to this exclusive meeting.

Her gaze shifted to a brooding merwoman who would fit well in a medieval fantasy video game. She sported an impressive scar on her cheek. Except for her length, the wiry frame and short haircut made her resemble an adult version of Oomie.

"Sagari," the merwoman said, her tone brusque. "Verala Sagari."

"Sagari is second in command and the chief strategist of this campaign." Mora nodded in her direction. "She's the Buva in charge of the Stingrays, our elite intel and commando unit."

As Dea inclined her head to the merwoman, her mind sailed back to the escapade in the Nautilus Chamber, where she first heard about the Stingrays. This was their leader—a Buva, no less. It was the highest rank of the military after Marabuva, held by Talmus Mora himself. The titles were derived from legendary mer-giants of Calliathron's folklore. If she felt they were too hyperbolic, Mora and Sagari proved her very wrong.

Lost in thought, Dea absent-mindedly traced the cables that snaked along the beams overhead. They converged on one side of the room, where a large screen covered one wall and displayed a map of the region. Three young merpeople sat by a bank of computers, and one was none other than Oomie.

Dea started. "How—"

The small mermaid gave her a wave, though it was suitably curt to fit the occasion. "Hey."

"Yes, my daughter is a technical lead," Mora's voice boomed. "Also a strategist. My son is also in this team. The last member of our think tank—other than Hal, of course."

Dea's eyes landed on the young merman to her right. It was obvious he inherited his heavy build from his father. So this is the guy they want to marry me to...

"Delighted to finally meet you," he said with a polite smile. "I work at MerTech."

"Pleasure making your acquaintance." She paused, wondering if it would be impolite to ask his name, given that they had already arranged for them to get married. "What do you do at MerTech?"

"Robotics and Technology Division."

"Anemon has been developing the drones for land exploration," Mora said, bestowing a half-smile on his son like he was the pearl of his eye. "And helping the engineers here with the latest Mizukami subs."

"Mizukami subs?" Dea asked.

"We will get to that in a short while." Mora checked the mini panel on the tabletop. "Hal is here."

Heads turned as the door slid open and Hal Moray Massa swam in. Ripples radiated out and lapped against the chairs.

"I do apologize for my lateness," Massa said, taking his seat at the round island.

"It's all good," Mora replied. "We were making a few introductions."

Massa nodded. "Shall we begin?"

"Certainly."

That moment, Dea couldn't help dwelling on the fact that within this one tactical room, eight individuals would brainstorm and unleash the historic strategy that would take down Serendiva.

Talmus Mora gestured to Oomie and then tapped on the tabletop. It came alive, replicating the map on the screen.

"Your information has been most useful, Dea." Mora swiped at the display and zoomed on a region close to the coastline of Serendiva. "We've managed to pinpoint the location of the facility, thanks to the efforts of the Stingrays, as well as Oomie. Over to you, Sagari."

The merwoman leaned forward, arms crossed on the table. "It's indeed an island. You can see it right here."

She jabbed at the small landmass and blew it up to maximum scale. All eyes bored into it.

A grey block occupied most of the island, surrounded by fortifications of both natural and human-made origin. The building was featureless except for a helipad.

"I'll start with a quick overview of how we found it," Sagari said, sharp eyes darting from one to another. "We've been listening in on human communications, but even in the encrypted channels that we've managed to tap, there's been no mention of the place. So the words Kadol Doova led us on this new search."

"Dilip Goonewardane mentioned it while I was present," Dea said flatly. "He probably didn't expect me to escape."

"It was a stroke of luck that he did." Sagari nodded. "Kadol means mangroves in their language, which is Sinhalese. And Doova means island. There are many islands with mangroves around Serendiva, but when we deciphered human maps, we found this specific island that went by that name. Then our reconnaissance mission sent us new intel. It's heavily guarded, and there's no doubt that this is what we're looking for."

"Excellent," Massa said, eyes gleaming.

The merwoman continued, "As you can see here, it's impenetrable due to those rocks, mangroves and the human-made wall on its perimeter. The only way in is through this dock and the helipad. To breach this fortress, we would first have to disable the sentinels and defenses at the dock. Anemon, the Mizukami subs can help here?"

"Indeed they can," Anemon Mora replied. "They come equipped with flying scud bots. They're good for surveillance and can also be used for scrambling signals and administering soporifics."

"We will go over it in detail. But first, I must mention that this facility is occasionally visited by Dilip Goonewardane—as well as other higher-ups of Serendiva. In fact, we've successfully managed to uncover a scheduled lockdown and heightened security in four weeks' time."

"And that is the time we must strike," Mora said grimly and looked at Massa. "If we capture Goonewardane, we are in a position to make demands of the human government."

"This will be phase one of our offensive." Massa leaned back. "Sagari, we will set up a covert operation to infiltrate Kadol Doova and capture Dilip Goonewardane. Once this objective is complete, this team can join the main force that will be on standby within sight of Seren City. Should the humans detect our presence, they will deploy their navy, which is considerable according to our estimates. They also possess large warships. They are still no match for us—we have the upper hand at sea. Even better, Mora told me about this key location—these straits to the north of Seren City."

"I must raise a concern here," Anemon spoke up.

"Yes?"

"Our fleet and infantry are equipped for naval battle—to lay siege to their coastal capital. But the covert operation you speak of would require land units with superior tech and capabilities. We would have to start integrating brain-machine interfaces for units to effectively engage in battle while maneuvering on land. Testing these systems, building prototypes and mass producing them for land teams would be impossible—not in four weeks."

A silence descended on the group, the momentum stilled by the undertow of Anemon's words.

Dea spoke up, her clear voice rippling across the air, "I may have a solution to that."

Eyeballs swiveled in her direction, and surprise flitted over many faces. In the vast void of hollowness inside her, something stirred—and it wasn't the scorching heat of anger that had bubbled up frequently during the course of the week. Dea clenched her jaw.

"And what is that?" Massa asked, eyebrows raised.

"First of all," she said, forehead furrowing, "I had no idea we were amassing weapons and units to 'lay siege' to Seren City. When did this start?"

"Recent events made it inevitable that we would go to war with humans—it was a matter of when." Mora's eyes shadowed under pinched brows. "They were inching ever closer to the atoll. This was kept under wraps in order to avoid an incident of mass panic. This is why military service is still mandatory for citizens. We certainly have been preparing."

She was quiet for a heartbeat. "These weapons systems you speak of...and these new subs. There's been no mention of them anywhere—not even leaked information. Where are they?"

"I've been meaning to see them myself," Oomie chimed in, throwing a glance at Mora.

"Very well." Mora looked at Massa, who gave him a nod. "Let's take a quick tour of our arsenal, so that all of us are on the same page."

"That sounds good," Anemon said, smiling at Dea, though it elicited no reaction from her.

"I have a few things I need to discuss with Sagari and Prof. Sevaler," Massa said. "We'll reconvene after a short break."

Talmus Mora led Dea, Oomie, Anemon and Prof. Soma to the bank of elevators. No one spoke along the way. They descended to the ground floor and entered a glass tube of a tunnel. In the deepening teal outside, lamps blinked on and emanated a chartreuse glow.

As they swam along, the tunnel branched and slithered along the seafloor, carpeted with white gravel. Dea involuntarily conjured up an image of soldiers training out in the waters. Eventually, they arrived at a heavily guarded structure that curved beyond view. The soldiers on duty saluted Mora and withdrew.

She still couldn't visualize how military submarines and weapons could be stored there on the border of the base, let alone tested or deployed. Talmus Mora leveled his eye at a retina scanner, and an inner door hissed open. Directly ahead was a window wall that looked out into what lay beyond.

Dea jolted to a stop. Oomie reacted the same way.

The "structure" was merely a barrier that circled around a gigantic hole in the seafloor. It was midnight blue, hinting at fathomless depths. A short tunnel, crusted with glass, jutted into it and ended at a bowl of an elevator, which brought to mind a DSV. Its shaft disappeared down into the hole.

"What is this?" Dea whispered.

"It's called a blue hole," Mora replied, leading the small party through the tunnel. "It's essentially a sinkhole. Ours is not the only atoll to have one."

"How is it formed?" Oomie asked in a hushed tone as they took their positions in the elevator. "It looks incredible."

That instant, it was as if they were suspended above a yawning chasm that extended all the way down to the bowels of the Earth.

Anemon hastened to explain while his father tapped an authorization code on the elevator panel, "A coral atoll comes into existence when a seamount sinks beneath the surface and leaves behind a fringing reef. Our submerged seamount has a cavern system. The roof of a cave had collapsed, causing it to open into the surface. The result is this sinkhole."

"So we're heading to the caverns?" Dea asked while the elevator started sinking. "It's converted to a...weapons arsenal?"

"That's right. It also opens out into the ocean beyond the atoll, so we can deploy our subs." Anemon smiled and spyhopped higher, his back ramrod straight. "My secret tech cave is also there."

In the corner of her eye, she watched Oomie roll her eyes at her brother.

Another guy playing with bots in the deep. It triggered a memory of a think room by a brine lake, and Dea hastened to extinguish it.

Silence fell again as they plunged down into the hole. Lights turned on in the elevator, but the halo of its glow was too weak to penetrate the blackness.

"How deep is this?" she asked, the words pulsing loudly in her ears.

"Over a hundred meters." Mora's resonant voice rumbled. "It's anoxic and barren at the bottom. The cavern opening is not located that far down."

As they steadily descended, an array of pinpricks appeared in the depths, and it soon transformed into a beacon that made them squint. The elevator eased to a stop, causing tiny waves on the surface of its interior pool. As soon as the doors beeped open, Mora swam out into the adjoining tunnel. Everyone followed behind.

It wasn't long before the company arrived on a platform. Dea's eyes soaked in the view.

Laid out before her was a humongous cavern, partially inundated and smothered with scissor lifts, cranes and swim-tubes. Hewn rock melded with concrete, and stalactites hung down from the roof.

What grabbed her attention was the colossal submarine at the center. Engineers and drones scurried around it like remoras on a blue whale.

"That's a Mosasaur class, nuclear-powered war sub," Mora said, placing his arms on the water barrier as he gazed ahead. "It can launch ballistic missiles with nuclear warheads from a range of five-thousand kilometers. This will help set Calliathron on the world stage as a formidable power. Serendiva will cower before our might."

Dea's eye landed on a small craft to the side—a mere goby fish next to the monstrous bulk of the Mosasaur. "Is that the..."

"Yes, that's a Mizukami sub." Anemon smiled. "Good for a small squad. It also acts as a mothership for scud bots. Everything is set for us to win this war."

"Not everything."

Multiple eyeballs focused on her. She raised an idle hand and touched the wound on her scalp, now healed into place.

Anemon recovered. "Oh, yes, the land machines. We will have to expedite our—"

"There's someone who's a few steps ahead in that area," Dea said tonelessly, though her tail flukes tapped a monotonous beat against the water barrier.

"Who would that be?" Mora asked, surprise oozing from his tone while his son just stared at her without a word.

"The Sea Witch."

Location: Blue Hole

https://youtu.be/9S1GuFI3k_E