One possible plot could be that Naruto, through some sort of magical or cross - dimensional event, ends up in the One Piece world. His ability to control the ocean could startle the pirates and marines alike. Maybe he teams up with the Straw Hat Pirates. He could use his ocean - controlling powers to help them navigate through dangerous waters, like the Calm Belt. He might also use it to fight against powerful enemies, like the Yonko, by creating huge tidal waves or whirlpools.
The plot could involve Naruto being seen as a threat at first. Since his power over the ocean is something unheard of in the One Piece world. However, as the story progresses, the characters realize his good intentions. He could use his power to find hidden islands or treasures that are submerged underwater. And his presence could disrupt the balance of power between the different pirate crews and the World Government. For example, he could block the Navy's ships from advancing by creating barriers of water.
In fanfiction, if Naruto was born in One Piece, he could bring a new style of fighting. His speed and agility from being a ninja would give him an edge in combat. He could run across the masts of pirate ships like he runs on trees. His Sage Mode could be related to some kind of ancient knowledge in the One Piece world. And his strong willpower would fit right in with the characters in One Piece who often have to face great challenges. He might even inspire some of the characters to be more selfless in their pursuit of their dreams.
One possible plot could be that Naruto and Kushina are somehow transported to the One Piece world. Naruto, with his powerful ninja skills, might team up with Luffy's crew. Kushina could use her chakra chains to help in battles against the various pirates or marines. They might be on a quest to find a way back to their own world while also getting involved in the major events of the One Piece universe like the search for the One Piece itself.
Well, one possibility could be that in this fanfiction, Naruto is somehow transported to the One Piece world and is banished by the World Government because they see his ninja powers as a threat. He then has to team up with the Straw Hats secretly to take on the World Government while hiding his identity.
One possible plot could be that Naruto discovers a new jutsu that allows him to control scorpions. He then uses this ability to gather intelligence in the Hidden Sand Village where scorpions are common. The scorpions could act as his little spies, reporting back to him any suspicious activities.
One idea could be that the Straw Hats end up in the Naruto world. Luffy might befriend Naruto and they could team up to fight a common enemy like Akatsuki members who are after some powerful Devil Fruits that have mysteriously appeared in the Naruto world. Zoro could have duels with some of the skilled sword - users in the Naruto universe, like Sasuke or Killer Bee when he uses his sword - like Samehada.
Perhaps in this fanfiction, Naruto is on a mission in his own world when a strange portal opens and leads him to the One Piece universe right where Robin is. At first, they are both cautious of each other. But as they learn about their respective powers and goals, they decide to join forces. Maybe there's a common enemy that is threatening both the ninja world and the pirate world, and together they strive to defeat it.
A plot could involve Naruto being mistaken for a powerful pirate in the One Piece world. Nami, seeing an opportunity, decides to join him for a while. As they journey together, they learn from each other. Naruto learns about the value of gold and jewels from Nami, while Nami is impressed by Naruto's never - give - up spirit during battles.
Well, it could start with Naruto mysteriously being transported to a cosmic dimension. As the father of the universe, he first has to figure out what that means. Maybe he has the ability to create new planets or life forms. He might meet some of his old friends in new forms in this universe. He could use his sage mode to sense the energy imbalances in the universe and work towards restoring harmony. His character development would be interesting as he goes from a village hero to a universal savior.
Well, one possibility could be that Naruto enters the world of Grimm. Since he has his ninja skills, he might initially be confused by the Grimm but then start using his jutsus to control them. Maybe he uses his shadow clone jutsu to surround and corral the Grimm, turning them into an army of his own. He could use his chakra to influence their behavior, like making them attack his enemies instead of the innocent.
One possible interesting plot combination could be that Naruto, with his Juubi powers, somehow gets transported to the One Piece world. He might team up with Luffy and his crew. Naruto could use his shadow clone jutsu to help in battles against the pirates or the Marines. His ability to sense chakra could also be used to detect hidden treasures or enemies with unique powers in the One Piece world.