Perhaps it has a prophetic significance. Maybe the trident is going to be crucial in some future event that Percy has to face. It could be the key to defeating a great evil or saving the demigod world. Poseidon gives it to Percy in advance so he can be prepared for what's to come.
The trident might represent Percy's growth. It could mean that he has reached a new level in his development as a demigod, and Poseidon is acknowledging that with this gift. It's like a rite of passage in a way.
In Percy Jackson fanfiction, a trident tattoo could symbolize a connection to Poseidon. It might mark a character as a demigod related to Poseidon or as someone with a special mission or allegiance to the sea god. Maybe it's a sign of power, as the trident is Poseidon's main weapon.
Well, it could be that Poseidon's Trident has been stolen and Naruto is called upon to find it. He teams up with some of Poseidon's loyal servants or maybe even a mermaid or two. Along the way, he uses his ninja skills to track down the thieves. When he finally finds the Trident, he has to face the main villain who stole it. Naruto might use his Rasengan in combination with the power of the Trident to defeat the bad guy and return the Trident to Poseidon.
In fanfiction, 'Poseidon Protects Percy' can be a central theme that shows the strong bond between father and son. Poseidon, as Percy's father, has a divine power to safeguard Percy in various dangerous situations that Percy often gets into in the Percy Jackson universe. It could also symbolize the idea of family protection and the power of the divine in a fictional context.
It might make Percy more confident. With the trident, he has a powerful symbol of his father's support. He could use it to face stronger enemies and gain more respect in the demigod world.
It could be a sign of his protectiveness. Percy cares about Annabeth deeply, and the jacket is a physical way to shield her from the cold, just as he would shield her from danger in a more serious situation.
He might become an even more powerful figure. The trident could enhance his abilities to control water and perhaps give him new powers related to the sea. He could use it to defend his friends and fight against stronger enemies.
One possibility is that Percy uses the trident to explore uncharted areas of the ocean. He discovers ancient underwater ruins that are protected by powerful magic. With the trident, he can navigate through dangerous barriers and uncover secrets about his own heritage and the history of the sea gods.
Naruto might initially struggle with the power of the Trident. Since he's used to his chakra system, the magic or divine power of the Trident would be something new. He could start by accidentally activating some of its basic powers, like creating small whirlpools or summoning small sea creatures. As he spends more time with it, he would learn to control it better, maybe even combining his own ninja techniques with the Trident's power, like using the Rasengan while channeling the Trident's energy through it.
The significance could be that it shows Poseidon's care for Percy. Despite being a god, he takes the time to visit his son at Camp. It could also signify that Percy is in for some big challenges, and Poseidon is there to prepare him.
In some fanfictions, Percy might obtain the trident through a special quest. Maybe he has to prove himself worthy to an ancient sea deity who then bestows the trident upon him as a symbol of power and trust.