There could be an old sea witch. She lives in a cave at the bottom of the ocean and knows all kinds of ancient magic. She's not necessarily evil but is very self - interested. Percy has to bargain with her to get some crucial information or a magical item. Also, a group of mer - children who idolize Percy. They follow him around and get into all sorts of trouble, but they also have some hidden talents that come in handy during Percy's adventures.
How about a selkie who has lost her pelt? Percy finds her and helps her look for it. She has a mysterious past and connections to some of the older sea spirits. She can also transform into a human - like form and has unique powers related to the tides. And then there's a sea dragon who is different from the usual ones. He's intelligent and can speak in riddles. Percy has to figure out what he wants in order to get his help on a mission.
A mermaid scientist. She could be researching the effects of human pollution on the sea and teams up with Percy. She has a very logical and in - depth knowledge of the sea's ecosystem but is also curious about the world above water. Another character could be a young sea godling who is trying to prove himself. He's a bit of a troublemaker and at first clashes with Percy but later becomes an ally.
How about a character named Riven? He is a young boy who was abandoned near a river and was adopted by the river spirits. He has the power to communicate with fish and other river creatures. Riven is initially very distrustful of Percy because he sees Percy as an outsider. But as they get to know each other, they become friends and Riven helps Percy understand some of the more hidden aspects of the rivers, like the places where the rivers' memories are stored.
Obviously Percy himself would be the main character. But there could also be sea nymphs like Amphitrite who could play a big role in raising him. Maybe Triton, son of Poseidon, could be a mentor figure to Percy.
Well, you could have a plot where Percy is sent on a quest to find a powerful artifact that has the ability to control all sea currents. Along the way, he meets a group of pirates who are also after the artifact for their own greedy reasons. He has to outwit them and deal with the challenges of the deep sea, like deadly whirlpools and giant sea serpents, all while trying to keep the artifact out of the wrong hands.
There could be a demigod who is the child of a minor god that we haven't seen much in the original series. For example, the child of Hebe, the goddess of youth. This character could bring a fresh perspective with their powers related to rejuvenation and vitality.
A demigod with the power to control time could be really interesting. They could either help or hinder Percy on his quests. Another could be a half - human, half - nymph who has a special connection to the natural world and can communicate with plants and animals in a way that Percy can't. There could also be a demigod from a far - off land who has different fighting styles and beliefs compared to Percy.
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.
A new character could be a half - angel, half - mortal who becomes Percy's ally or rival. They have powers related to both the Christian concept of angels and the Greek demigod powers. Another could be a seer from an ancient, long - forgotten civilization who has knowledge about Percy's true potential as a son of god.
One great 'Percy Jackson Sea Prince Fanfiction' is 'The Sea Prince's Ascent'. It really delves into Percy's newfound powers as a sea prince. The author does an amazing job of describing how Percy navigates the complex underwater politics. Another good one is 'Percy, the Sea Prince and the Quest for Atlantis'. It combines the adventure elements typical of the Percy Jackson series with Percy's role as a prince of the sea.
There could be a new demigod who transfers to Percy's college. This demigod could have powers related to nature, like being able to make plants grow instantly. They would become Percy's ally in dealing with the campus - based mythological threats. Another new character could be a strict dean who is always on Percy's case, not realizing that Percy is actually protecting the college from real danger. And there might also be a mysterious janitor who actually has a deep connection to the underworld and gives Percy cryptic warnings from time to time.
A new character could be a transfer student from another demigod camp. This student has a different set of powers and a unique backstory related to a less - known Greek god. They could initially clash with Percy but then become great friends as they face challenges together.