Perhaps in the fanfiction, Poseidon has to raise Percy in secret from the mortal world. So he enlists the help of some friendly sea nymphs and mermaids to take care of Percy when he can't be there. And as Percy grows, he starts to show signs of his powerful abilities, and Poseidon has to figure out how to train him without attracting too much attention from the wrong people.
One possible plot could be Poseidon teaching Percy about his underwater powers in a really fun and father - son way. For example, they could have little adventures in the ocean where Poseidon shows Percy how to communicate with sea creatures. Another plot might involve Poseidon protecting Percy from the other gods who are jealous of Poseidon's special relationship with his son. Maybe he creates a hidden underwater lair for Percy to grow up safely.
A great plot could be Poseidon trying to raise Percy while also dealing with his own godly duties. This could lead to some comical situations like accidentally missing Percy's first steps because he had to attend a sea - god meeting. Also, Poseidon might try to give Percy a normal life on land, but Percy keeps getting into trouble because of his half - god nature, and Poseidon has to bail him out.
A great plot might be that Poseidon has to protect baby Percy from other mythological beings who sense his potential power. So he hides Percy in a special place where only he can find him. This could lead to all kinds of adventures as Poseidon has to fend off threats while keeping Percy's existence a secret.
In this type of fanfiction, a possible plot is that Poseidon raises Percy away from Camp Half - Blood to protect him from the prophecy. As Percy grows up, he becomes more in tune with his water powers. He could then have adventures in the ocean, like finding lost civilizations or facing off against sea monsters that Poseidon sends his way to test him.
One interesting plot could be Percy having to prove himself to Poseidon in a new and unexpected way. For example, he might have to solve a mystery that is directly related to Poseidon's power over the sea but in a realm that is unfamiliar to both of them, like an underwater civilization that has been lost for centuries.
In some versions, Poseidon might keep Percy's mother at a distance to protect her from the wrath of the other gods. He could send her gifts secretly to let her know that Percy is okay. For example, he might send a magical seashell that can communicate with Percy.
In fanfictions, Poseidon often interacts with baby Percy in a very gentle and protective way. He might use his powers to create a safe environment for Percy, like a special underwater grotto where Percy can be hidden from danger. Sometimes, he sends sea creatures to watch over Percy, like dolphins or friendly sea nymphs.
One interesting scenario could be Poseidon using his powers to create a mini - underwater world for baby Percy to explore safely. He might make colorful fish swim around Percy and gentle sea currents act like a cradle.
One idea could be Percy as a baby having small adventures in the underwater world of Poseidon. Maybe he befriends a baby sea monster. Another could be Poseidon trying to protect baby Percy from the other gods who are suspicious of this half - god baby.
Another plot could involve Percy discovering a hidden connection between Poseidon and Athena that was long forgotten. This could lead to a situation where he has to convince the other demigods that this connection is important for the future of the camp. Maybe there are ancient prophecies that only he can understand due to his unique parentage.
A plot could also center around the baby's identity and how it fits into the existing world of Percy Jackson and the Olympians. The baby might be seen as a symbol of a new era, a bridge between different pantheons perhaps. And it could face difficulties in being accepted by both the mortal and the divine worlds.
Their relationship would likely start with Poseidon being a strict but loving father. He would teach Percy the ways of the sea and the power that comes with being a son of Poseidon. As Percy grows, they might have some disagreements, for example, about how Percy should use his powers in the mortal world.