Drippy led Twilight and her friends through the current. Twilight's sea pony body was sensitive to the feel of the ocean, her ears had a sonar-like reception and her eyes could see clearly through the murk. Her friends had adapted quite well to being sea ponies too it seemed. Rainbow Dash had been eager to see how fast she could swim, Pinkie Pie was enjoying doing sommersaults, Applejack and Rarity were asking Drippy about life under the sea and Fluttershy had made friends with several schools of fish that had swam by.
"Well, Princess Tidellia has ruled for at least a thousand years. I don't know where we would be without her." Drippy said, answering Applejack's question. "We have some contact with surface ponies but mostly Seaquestria's stayed the same as long as I've been a mail carrier."
"Twilight?" Rarity asked. "Do you think we could visit Seaquestria while we're down here?"
"We're not here to do any sight seein'. In case you forgot, there's some emergency we've got to fix first." Applejack said, trying to focus her friend on the task at hand. The group swam onward under the waves, heading deeper into the ocean depths. Twilight looked over her shoulder. Rainbow Dash, Fluttershy and Pinkie Pie were behind her, chatting amongst themselves. The shoreline behind them disappeared into the darkness of the sea.
"The floor quakes started about a week ago but they were over pretty quickly," Drippy said.
"Are the floor quakes the problem? Have they caused much damage?" Twilight asked.
"No, they did stir a few things up but the occaisonal quake is nothing out of the ordinary. Prince Slipstream and his friends found something on the edge of the Everflow Forest that's caused all the commotion."
"What did they find?" Rarity asked.
Drippy had to stop and think. "It's... ummm, well at first we thought it was Canterlantis, a mythical lost city where sea ponies and the other tribes all lived together. But this city's... it's different."
"Different how?" Twilight asked. "If Canterlantis is a myth, how do you know this place you've found isn't it?"
"Umm, you just kinda have to see for yourself. We even found two creatures who were living in it. They called it Rapture and said it was from the surface."
Twilight thought. "I've never heard of a city called Rapture on the surface of Equestria."
"Oh!" Drippy remembered. "They said it was from the surface of ANOTHER world."
"Another world?" Applejack repeated. "You mean another Equestria?"
"Well, to be honest, I only know what I've heard. They just told me to go get you guys so I don't really know that much."
A city from another world? Drippy's story seemed more science-fiction than anything else. But considering Twilight and her friends were currently sea ponies swimming through ocean, she had to believe it was at least possible.
The seven sea mares continued their progress through the ocean passing over coral reefs, trenches and a few other unremarkable undersea landmarks on the ocean floor. A few larger sea creatures passed them as they continued on, a couple whales that dwarfed Twilight Sparkle's balloon swam by them. Fluttershy tried to talk to them as well but it seemed they had some place to be too.
Finally, Drippy led them to the edge of the ravine. Twilight thought they were close to the surface at first because she saw light peaking over the Cliffside in the distance. Getting closer though, she realized that the light was coming from the sea floor.
"Well, here it is. Rapture," Drippy announced.
"Oh... my word, it's beautiful," Rarity said, enamored. The city of Rapture occupied all the visible ocean floor before them. It was massive, buildings of all shapes and sizes connected by tubes spread out in tightly packed rows. Twilight actually thought a few of the structures resembled buildings she'd seen in Equestria, pictures of Manehattan. Submerged skyscrapers towered in the center of the city, lights on the buildings illuminating the sea and space around them.
Two other sea ponies swam into view carrying with them some kind of bubble. They sat down the clear sphere right next to where the other sea ponies arrived.
"Drippy!" one of them asked. "Those our friends from the surface?"
"Yep! All six of them," Drippy said as they approached. Twilight had heard about sea pony magic. They had the ability to manipulate pockets of air into bubbles that could sustain oxygen-breathing life forms underwater. Twilight saw two life forms she'd never encountered before inside the bubble in front of them.
"Great, maybe they can help us out here. All right, thanks for your help Drippy. I think Tide Turner's waiting for you back at the shop," one of them said to Drippy.
"Okie dokie. Best of luck you guys!" Drippy said, swimming off.
"Twilight Sparkle? From Canterlot?" one of the ponies asked.
Twilight nodded. "Yes, I'm Twilight Sparkle and these are my friends, Rainbow Dash, Pinkie Pie, Applejack, Rarity and Fluttershy."
"I'm Slipstream and these two in the bubble are Albert and Claire. Rapture is there home."
"Doctor Claire Grace and my partner, engineer Albert Harmon," one of the creatures said in a female voice.
"And Rapture is a very dangerous place. But it is also our home... and we very much want to save it," the male said.
Slipstream nodded. "Rapture is apparently the source of the floor quakes recently."
"Yes, Princess Celestia sent us here to investigate some kind of disturbance," Twilight explained.
"Well, you're looking at the disturbance right in front of ye," the other sea pony said as he moved out from behind the bubble. Twilight was surprised again; it was a sea pony wearing some kind of diving suit.
"My name's Ebbin McFlow and I am a sea pony," he said in a thick Irish accent. Ebbin appeared to be a green sea pony with a white mane and small beard. He wore a diving suit with four hooves and a bubble helmet. Twilight couldn't imagine walking on the sea floor but here was another pony, a sea pony simply walking over to them.
"Ye'll 'ave to forgive the apparatus I'm wearin, special model. We've been tryin' to investigate whataver this thing is fer the pahst couple of dehys nouw," Ebbin explained.
"Wait a minute," Rainbow Dash stopped him. "If you have these diving suits, why did we have to turn into sea ponies to get down here?"
"Well, as Ebbin pointed out, his 'apparatus' is a special model, meaning he's the only one with one. He built it himself a couple years ago and he's actually been on the surface with it," Slipstream explained.
"What's the matter Rainbow? Missing your wings already?" Pinkie teased, doing a backflip.
"Listen to me," Albert said to the ponies. "Rapture is a very dangerous place. There are people in there that have... changed. There's chemicals in the city that turn people into monsters. There's violent weapons, security systems and traps."
Claire stepped forward. "Albert and I were attacked. The city right now is under the control of one man, Trent Arnold, our boss. We were contracted by him..." Claire trailed off at that as if thinking back.
Albert stepped in. "He recruited us to cure the city's addiction to ADAM, the substance that's destroying the inhabitants. We created a cure of sorts, something that neutralizes ADAM's effects but that's not all Trent wanted us to do. He wants us to add a chemical to the cure when it's distributed, an agent that will make the people obey him without question."
"He's pretending to do the right thing, claiming to help when really all he wants is control," Claire added. For a moment, both the bipeds stood in the bubble and said nothing, their twin gazes looked out somewhere over the city as if seeing a future over the aquatic horizon.
"So... y'all want us to save your town?" Applejack asked.
"I can't ask any of my kingdom's own citizens to do this. Seaquestria has always relied on our ability to manipulate the ocean to protect us but our powers our useless without water. Inside that city, even in a diving suit, we would be defenseless against the perils within," Slipstream said.
"So you called us for help," Twilight filled in the gap. Slipstream nodded.
"New neighbors move in and they've brought all their troubles with them. Nothing new, really," Ebbin summarized the situation.
"But... Twilight's spell. We could be stuck as sea ponies," Rainbow Dash sounded worried.
"To be honest, I don't know the full details of the spell," Twilight explained. "There's a chance that if we're just outside of water, we'll change back."
"Well... isn't that convenient," Rarity said, grinning nervously. Truth be told, they were all a little more than afraid of remaining sea ponies on a permanent basis. The safety of Equestria came first though, they knew this as the Elements of Harmony. Sometimes the cost was high... they just hoped it was never too high.
"The only way we'll find out is if we get going," Twilight said.
"Right then. I'll lead you into the city. Follow closely, formerly legged ones," Ebbin said. The six sea mares followed the walking sea pony, a stranger set of circumstances they never found themselves in as they headed into the glow of the city in front of them.