Percy could discover ancient and forgotten temples or shrines in the wild. These could hold powerful artifacts or be the lairs of minor gods or spirits. He might have to face various traps and puzzles to explore them fully. In the process, he would rely on his skills as a demigod, like his ability to control water, to overcome obstacles and uncover secrets. This would be an exciting addition to the fanfiction as it would add new elements to the Percy Jackson universe.
In the wild, Percy might have to learn to survive without the conveniences he's used to. He could struggle to find fresh water, build shelters, and hunt for food. This survival aspect would test his physical and mental strength. Maybe he would also form an alliance with some wild animals, using his special connection with them (since he's a son of Poseidon, he has a way with sea creatures, and this could extend to some land animals in the wild) to help him in his adventures.
Well, he could encounter unique mythical creatures that are specific to the woods. Maybe he'll find a hidden grove protected by dryads where he has to prove himself worthy to enter. It could also be that he discovers an ancient magic in the woods that helps him in his quests.
He might discover new sea creatures that are unique to Atlantis. Maybe he'll find a hidden school of magic there, or encounter ancient sea gods who have been forgotten by the outside world.
He could be involved in some really cool quests. Like finding some ancient artifact that's hidden deep within Olympus. He'd probably make new friends among the minor gods and goddesses. And of course, there would be the constant threat of some ancient evil trying to take over Olympus, and he'd be right in the middle of the fight to defend it.
In the fanfiction, living in the sea could give Percy a chance to explore the secrets of his water - related powers more deeply. He could learn to control the tides in a more precise way or communicate with the very essence of the ocean. He might also face challenges such as dealing with underwater magic that is different from what he's used to on land. There could be ancient sea spells that he has to decipher in order to save the sea from a dark force.
His relationships with his friends from Camp Half - Blood might become strained as he's away from them for long periods. They could worry about him and feel left out of his new adventures.
Percy as a pirate captain would likely have a ship with special features. It could be enchanted in some way, perhaps having the ability to sail faster than normal ships due to some demigod - related magic. His cabin on the ship might be filled with mementos from his previous adventures on land, like a trident he once found or a piece of armor from a defeated monster.
In some fanfictions, the Nemean Lion might be given more human - like intelligence. So, Percy has to outwit it rather than just relying on his physical strength. He could use his knowledge of Greek mythology to find the lion's weakness that others don't know about.
Well, he might discover new magical creatures unique to Atlantis. Maybe he'll form an alliance with some underwater beings to protect Atlantis from an unknown threat.
He could encounter rare mythical creatures that are only found in the deepest parts of the wild. For example, he might come across a group of centaurs who have a different culture compared to those he met before. These centaurs could teach him new survival skills and ancient lore.
One possible fanfiction could be about Percy having a mysterious encounter with Nyx in the Underworld. Maybe he stumbles upon her realm while on a quest and has to face her challenges.