Some fanfictions might explore Percy's relationships in this underwater setting. For example, how his friendships with Annabeth and Grover change. Maybe he makes new friends among the underwater beings. Also, there could be a plot about Percy protecting the underwater world from a new threat that is specific to that environment, like a powerful and evil sea monster that is causing chaos among the underwater civilizations.
In 'Percy Jackson lives underwater' fanfiction, it could also involve Percy's family. His father Poseidon might play a more prominent role. Percy could learn more about his heritage and powers from his father in this underwater realm. There could be a story about Percy training with other demigods who also have an affinity for water, and together they form a special team to face challenges in the underwater world.
Obviously, Percy Jackson himself is a main character. He's the one living underwater in these stories. Annabeth Chase might also be a key character as she's Percy's close friend and often involved in his adventures. Grover, as Percy's satyr friend, could also be featured, perhaps trying to visit Percy underwater in some way.
One idea could be a fanfiction where Percy and his friends go on a new quest in a modern, urban setting. Instead of the usual mythological locations, they have to deal with monsters hiding in big cities. Another idea is a story that focuses on the relationships between the characters in a more in - depth way, like exploring the friendship between Percy and Grover during their off - quest times. And a third idea could be a time - travel fanfiction, where Percy gets sent back to the time of the ancient Greek heroes and has to interact with them while still holding onto his modern values.
One idea could be to explore Percy's life after he has fully mastered his powers. Maybe he goes on a quest to find a long - lost relative who also has demigod powers. Another could be a story where Percy and his friends have to deal with a new type of monster that is immune to their usual weapons and they have to find a creative way to defeat it.
One interesting plotline could be the characters from different parts of Percy Jackson's world suddenly finding their lives intertwined in unexpected ways. For example, demigods from different camps having to team up against a new, powerful threat that targets all of them regardless of their origin.
The theme of self - discovery is also common. When Percy is underwater, he is often in a different environment from his normal life on land. This new setting makes him face new challenges and learn more about himself. He might discover new powers or aspects of his personality that he didn't know before. It's like the underwater world is a mirror for him to understand himself better.
Perhaps in the fanfiction, Percy could experience a mental collapse. This could be due to all the pressure and trauma he has faced over the years. His friends might have to find a way to bring him back from this dark place, and in the process, we could see deeper relationships develop among them. For example, Annabeth could use her knowledge and their shared history to reach Percy on a different level.
Another concept could be that a powerful ancient evil is affecting both the Percy Jackson universe and Arendelle. Elsa and Percy are the only ones who can sense it at first. They must team up, traveling between their two worlds, to find the source of the evil. Along the way, they learn about each other's powers and cultures, and their combined powers are the key to defeating the evil.
One idea could be a crossover where Harry and Percy meet in a magical realm that combines the wizarding world and the world of Greek gods. They could team up to fight a common enemy, like a dark wizard who has also angered the gods.
One idea could be a fanfiction where a character gets a tattoo of Percy's sword, Riptide. The tattoo could have magical properties in the story, like glowing when danger is near. Another idea is a tattoo of the Camp Half - Blood logo. It could be a symbol of pride for a demigod character in the fanfic, and maybe it was given to them as a mark of their belonging to the camp.
Another interesting concept is a story where Percy Jackson is somehow transported to the Marvel universe. He could use his water - controlling powers in unique ways there. Maybe he'd join forces with Namor, the Sub - Mariner, and they'd have an underwater adventure together, facing off against some underwater threat that only their combined powers could handle.