If Naruto was the son of Poseidon in fanfiction, he might possess the power of hydrokinesis at an extremely high level. He could transform water into any shape he desires, like creating weapons out of water or forming impenetrable water shields. His connection to Poseidon could also give him the ability to manipulate water vapor in the air, allowing him to create fog or mist for stealth purposes or to disorient his enemies.
Naruto could have the power to communicate with sea creatures. This would be a really interesting addition to his skills. He could summon giant whales or sharks to help him in battles, just like how he summons toads in the original Naruto story. Also, he might have enhanced healing abilities related to water, which could help him recover from injuries faster.
He would probably have powerful water - based abilities. For example, he could control the oceans and large bodies of water like Poseidon. He might be able to create huge tidal waves or even walk on water effortlessly.
He might have the power of instant teleportation. Just like a god can appear anywhere, Naruto could do the same to surprise his enemies or reach his friends in need quickly.
He might have the power of Odin's All - Father magic. This could allow him to see the past, present, and future, just like Odin's ability to gain wisdom through his ravens. Also, he could potentially have enhanced physical strength, much greater than what he has as a regular ninja, allowing him to overpower even the toughest opponents with ease.
He might have the power of charm. Just like Aphrodite can make people fall in love with a glance, Naruto could have a natural charisma that makes people trust him and want to follow him more easily. It could be really useful in his mission to bring peace to the ninja world.
In this fanfiction scenario, Naruto would inherit a host of Saiyan powers on top of his ninja skills. For starters, he would have the Saiyan's natural fighting instincts and the ability to quickly recover from injuries. His power level would constantly increase as he fought, similar to how Saiyans get stronger through battles. His existing jutsus like the Rasenshuriken could be infused with Saiyan energy, making it not only cut through opponents but also blast them with a powerful ki - like force. And with his Saiyan tail, if he had one, he might have an additional form or power that was unique to him, perhaps something that combined the power of the Great Ape form with his Nine - Tailed Fox form.
He would have a whole range of powers. He could have the strength of Hercules to overpower his opponents. Also, the ability to control the wind like Aeolus from the Olympians. This would enhance his existing wind - style jutsu.
Naruto could inherit Frieza's ability to survive in space and extreme environments. Along with that, his Rasengan could take on new forms influenced by Frieza's energy. For example, it could be a purple - colored Rasengan with the destructive power of Frieza's attacks. He may also gain the power to transform like Frieza, with each transformation increasing his strength, speed, and overall combat capabilities.
He would likely have a combination of ninja powers and Asgardian powers. For example, he could still use his Rasengan, but it might be enhanced with Asgardian magic. He might also have superhuman strength and durability like the Asgardians, which would make him even more formidable in combat.
Maybe he has the power of a different tailed beast. Since Naruto has a connection with the Nine - Tailed Fox, his son could be linked to another tailed beast, which would give him a whole new set of powers and challenges. He'd have to learn to control this power, just like Naruto did with the Nine - Tailed Fox's chakra.
It's possible that he has the power to summon creatures related to Amaterasu. Maybe some sort of fire - spirit or a mythical beast associated with the goddess. And from Naruto, he could inherit the ability to enter Sage Mode, which would further enhance his combat capabilities when combined with his fire - based powers.
He could have the power of light. Maybe he could create blinding flashes to disorient his enemies. Also, he might be able to control the sun's heat, using it in combat like shooting out beams of intense heat.