Hello everyone! Just a few notes before we get to the story- I believe in the theory that Calypso's last name is Nightshade, like her sister, Zoë. (Which makes perfect sense to me.) So her last name is going to be Nightshade in the story. Deal with it. And if you don't like it, just ignore it.

Another thing. I don't really include the parents in this, but they might be mentioned if not directly shown. I'll try to keep the characters' stories as close as possible to the original concepts.

All couples created in here are cannon in the actual series, so no excuses for complaints on the subject.

Disclaimer: I do not own any Rick Riordan material or Disney's The Little Mermaid. Now on with the story.

Chapter 1

There were clouds in the sky. The sea was smooth. A thin fog shrouded the air in moisture. A giant ship sailed through the water, it's crew hard at work hauling up a net full of fish. Dolphins swam in the water alongside the vessel.

"Ah! Isn't this great? The salty sea air, the wind blowing in your face." Princess Annabeth jumped down from the bench, her grey skirt billowing in the wind. "A perfect day to be at sea."

Despite being royalty, Princess Annabeth loved working alongside her staff. Whenever she got the chance, she would pull back her curly blonde hair and set to work on projects. The very ship she was on had been built by her and the royal mechanic, Leo, who was one of her trusted friends.

She and her other trusted friends were helping the fishermen haul in the day's catch. Festus the mechanical dog (also built by Leo) ran around deck, licking the salty air.

"Yes." A girl with chocolate colored skin looked up from the side of the ship. "Really," she gulped, "Delightful." She pulled her curly hair back and leaned over the side again, hurling. Hazel had never really been fond of sailing.

A girl with choppy brown hair walked up to her and patted her on the back.

"A fine strong wind and a following sea! King Poseidon must be in a friendly type mood," one of the fisherman said.

"King Poseidon?" Annabeth asked.

"Ruler of the merpeople- thought you would know about him." The girl comforting Hazel looked up at the princess, a confused look on her face. Piper was Annabeth's first lady in waiting, and knowing so much about her, this was surprising.

Hazel looked back up. "Merpeople. Of course she wouldn't. It's just nonsense."

The fisherman picked up a salmon. "Oh, it's no nonsense, missy, it's the truth!" He struggled to keep hold of the fish, which flopped around in his hands. "I'm telling you, down in the depths of the ocean, they live alone!" The fish slipped from his fingers, flying overboard, down into the blue sea. The salt water engulfed it's scaly body.

The fish, still being alive, sighed, looking at the massive boat above. It turned around and swam down.

It weaved through a patch of seaweed and trailed past some colorful plants, the movement causing them to shrink back and hide away. The salmon swam with a group of angelfish, passed underneath a colony of free-floating jellyfish, and moved through crevices in the coral reefs. He approached a humpback whale with her two calves. His image reflected in her giant eye.

He swam off.

Mere seconds later, dark shapes came out of the depths. And, as they came into the light, they couldn't be mistaken.

From the waist up they looked like normal humans, with arms and round heads with hair. But from the waist down they had the tails of fish.

Merpeople, dozens of them, came up into the sunlit waters. They propelled themselves in one direction, swimming gracefully under and around the submerged rock formations, toward a place past the coral reefs. Once above a drop in the rocky sand, their destination could be seen.

Sitting at the bottom of the ocean was a giant castle, lit up with what looked like a thousand stars. The merpeople called it Atlantica.

They swam inside it, assembling into a room built like an amphitheater. At the bottom was a wide flat area, like a stage, and an unlit chandelier hung in the middle of the domed ceiling.

Once everyone had settled, conch horns sounded, and swordfish swam into the room, forming a line. A mermaid- who looked to be in her later twenties/early thirties- brought up the end of the line. A sash was displayed across her chest, showing that she was part of the royal staff. She gave a small cough. "His royal highness, King Poseidon!" she announced.

The crowd cheered as a carriage pulled by dolphins entered the room. The merman at the reins had dark graying hair that floated to his shoulders, and a beard that went down to his chest. He was holding a golden trident that glowed with power. As he passed the center of the room, he held it up and zapped the chandelier above, making it burst with light. The applause grew louder.

The mermaid spoke again, her white tail swishing. "And presenting the distinguished royal trainer, the radical, ingenious, crustaceous, Chiron!"

A smaller horn (that sort of sounded like a kazoo) was blown and Chiron the Crab entered the room. Chiron was larger and wiser than most crustaceans, giving off a sense of knowing to the other creatures. He too was in a carriage, but it looked quite small next to the King's. It was pulled by two goldfish, who bucked at the crab's reins. He steadied them and pulled up closer to the King.

"I'm really looking forward to this session, Chiron," King Poseidon said.

"Your majesty, this will be the the finest training session I have ever done. My pupils are sure to be spectacular-ARGH!" The goldfish jerked forward, making the carriage flip upside down. King Poseidon gave a small laugh.

"Yes, and especially, my son, Percy."

"Yes," Chiron said as he settled back down in his seat, "yes, he is, truly, the most powerful of them all."

King Poseidon smiled and directed the dolphins toward his balcony seat.

Chiron sighed and said quietly so that the King couldn't hear him, "If only he'd show up for a lesson, once in awhile."

His goldfish swam down to the center of the room, where he climbed out and grabbed a stick out of the carriage. Chiron used the staff while training his pupils, in order to help him direct their focus. He held it up for quiet, and the audience grew silent.

"Merpeople of Atlantica," he started. "I welcome you here today, to witness the strength and talent of Atlantica's youngest warriors in training." He flicked his staff at a group of sea creatures off to the side with instruments. They started a low drum beat.

"Let them prove their power to you." He turned away from the crowd and flicked his staff again. Light appeared in the last darkened area of the room.

It revealed five giant clamshells placed flat in a semi-circle, a sixth slightly higher in the middle.

"Mermaids and Mermen!" Chiron projected his voice. "I present to you Atlantica's youngest warriors in training." He pointed his staff to the shell furthest to the left and the music grew louder. The shell flew open and out swam a merman with raven black hair and an equally black tail. His skin was pale, and he brandished a Stygian black sword.

"Nico di Angelo," Chiron announced.

He pointed to the next shell and a mermaid with caramel colored hair and a red tail came out. The seashells she wore were the same scarlet as her fins. Her skin was milky white. A gold dagger was sheathed in a leather strap wrapped around her waist.

"Calypso Nightshade," Chiron said.

He then pointed his staff to the third shell in the middle. It too opened and another merman emerged. His black hair was cut short, military style, and his tail was a deep purple. Like the others, he held his weapon of choice, a bow and arrow. He notched an arrow in place, his muscles tense, prepared for anything.

"Frank Zhang."

Chiron pointed to the fourth shell and out of it came a second mermaid. Her hair was short and spiky, her tail and seashells a bright blue. She held a staff in her hand, and unlike Chiron's, it had a sharp point at the end. It seemed to spark with electricity.

"Thalia Grace."

Chiron pointed to the shell on the right end, and it revealed a blonde merman with close cropped hair. His tail was a bright blue, like Thalia's, and he had a small scar above his lip. He brandished a gold sword, and his eyes scanned the room.

"Jason Grace." Jason and Thalia didn't look much like brother and sister to most merfolk, but they had the same electric blue eyes. The crowd applauded the five teenagers, whose bronze armor glinted in the light.

"And now," Chiron's voice boomed across the room, quieting the audience again. "Let me introduce you all to a very special merman." He pointed to the sixth shell that rose above the others. The music reached it's climax. "Prince Perseus Jackson!" he announced as the shell opened up. But there was one thing...

It was empty.

Chiron and the teenagers gasped, and the crowd quickly followed suit.

"Oh boy," Jason said.

Nico face palmed himself.

"Not again," Frank sighed.

Chiron turned and looked up at the balcony where King Poseidon was watching with his other son, Tyson. A mixture of terrifying horror and anger was strewn across his face. His trident glowed with fury.

"PERCY!" he bellowed.

And there you have it. The first chapter in this epic crossover. It took me a while to decide on who would be mermaids or humans, and if Frank was going to have his staff or bow and arrows… And the tail colors, now that was a process. Especially for Frank and Calypso.

If I made any grammar errors that I missed in the editing process, please tell me so that I can correct them. And I would love your guys' opinions on the story so far, but please try not to yell at me. Subtle hints and suggestions will be accepted, but that doesn't mean that I will use the advice. I'm trying to find my own writing style, and if it interferes with that, then I probably won't use them. And, again, I'm open to all opinions and ideas.

Thank you very much, and spread the word about the story. I'm counting on you guys!

~Reader4ever1