Annabeth Chase would be a great character to include. She is smart and can help Percy with strategizing in difficult situations. Her knowledge of architecture and ancient history can come in handy when they are exploring new places in the ocean world.
Grover Underwood is also a good choice. His ability to sense nature and his loyalty to Percy can add a lot to the story. He could help Percy communicate with sea - related nature spirits or detect any threats to the ocean environment that are related to the land.
One interesting character to include would be a half - blood from the Ares cabin who has the power to control fire, named Ember. She could be both a friend and a rival to Percy. There could also be a centaur who is a bit of an outcast from the main centaur group and teams up with Percy. His unique perspective and skills could be very useful. And then there's Rachel Elizabeth Dare. Her ability to see through the Mist and her non - half - blood status could bring a fresh dynamic to the story, especially when it comes to Percy's new situation as the 'Son of Ares'.
Well, of course, you have to include Percy Jackson himself. Then, there could be a son of Dionysus, like Pollux. He could be a fun character to include as he already has his own experiences and relationships within the Camp Half - Blood. Chiron, the centaur mentor, would also be a great addition. He could offer wisdom and guidance to Percy and the son of Dionysus during their adventures. Another character could be Annabeth Chase. Her strategic mind could come in handy when they are facing difficult situations in the fanfiction.
Grover could be an interesting addition. Even though he's a satyr, his loyalty to Percy and his own unique skills could be put to good use in a sea - centered story. Maybe Nereids, the sea nymphs. They can bring an element of mystery and beauty to the fanfiction and might be able to help Percy in some way. Another option is Chiron, who could guide Percy from the shore in his sea - related quests.
Another plot could involve Percy having to deal with a powerful sea monster that is not from Greek mythology but from some other ancient culture's sea lore. He has to use his skills and the help of his friends in a new and different way to defeat it.
In Percy son of Neptune fanfiction, including Nico di Angelo would be interesting. His connection to the underworld could bring a new dimension to the story, especially when dealing with any threats or mysteries that involve both the sea and the underworld. Reyna could also be a great addition. Her leadership skills and combat abilities would make her a valuable ally or a formidable opponent, depending on the plot. And of course, Chiron, the centaur, who could offer his wisdom and guidance to Percy from afar, as he has so much knowledge about the demigod world.
A satyr who has a special connection to the minor god. He could be like Grover, but instead of being dedicated to Pan, he's dedicated to this minor god. He could help Percy understand the ways of the minor god and provide some comic relief as well.
One great Percy Jackson ocean - related fanfiction is 'Under the Sea's Secrets'. It delves into Percy's adventures specifically in the ocean depths, exploring new sea creatures and hidden realms. Another interesting one is 'Ocean's Call to Percy'. It focuses on how the ocean has a special connection with Percy, almost like it's guiding him on a new quest. And 'Percy and the Lost Ocean Treasures' is also good. It's about Percy's search for ancient treasures hidden in the ocean, full of action and mystery.
Annabeth would be a great character to include. She could use her intelligence to help Percy solve problems and strategize against their enemies in the underwater world.
The gods themselves could be interesting characters to include. For example, Poseidon could offer Percy more power or advice at crucial moments. Athena could also play a role, perhaps initially being an adversary because of her different goals, but later becoming an ally. Even minor gods like Hecate could be included. Her magic could be used to help Percy in situations where his normal powers aren't enough. Also, new characters created specifically for the fanfiction, like a powerful demigod from a previously unheard - of lineage, could add an element of surprise and freshness to the story.
Definitely include Percy and Annabeth. They are the central characters in the original series and their relationship and skills are key. Percy with his water - related powers and Annabeth with her wisdom and strategic thinking.