It could be a senior officer who has a grudge against Percy for some reason. Maybe Percy accidentally made him look bad in front of the higher - ups early on.
Another plotline could involve Percy making new friends in the navy. These friendships could be tested during dangerous missions or when faced with internal conflicts within the naval unit.
In 'bella joins the navy fanfiction', it could be that Bella joins the navy to follow in the footsteps of a family member. Once in the navy, she could be part of a special unit. There, she has to learn to work with her teammates, who may initially be skeptical of her abilities. But as time passes, she proves herself through her skills and determination.
Themes like duty and sacrifice are frequently seen. Percy has a duty to his country and the navy, and this might lead to him having to make sacrifices. For example, he might have to give up personal time or relationships for the sake of his naval responsibilities. Another common theme is growth. He starts as a certain type of character and through his experiences in the navy, he grows and changes, becoming more mature and capable. This growth can be both in terms of his skills as a sailor and his personal qualities.
One challenge Percy might face could be getting enough resources. In the north, materials for ship - building might be scarce. He may have to search far and wide for suitable wood or metal. Also, recruiting sailors in a cold and harsh northern environment could be difficult as not many people would be eager to leave the relative safety of their homes for a risky naval adventure.
One common theme is heroism. Percy, as a Navy Seal, is often shown as a hero, saving the day and facing danger bravely. Another theme is loyalty, loyalty to his team and to his country. For example, in many fanfictions, he will go to great lengths to protect his fellow Seals.
It could be a jealous friend. Maybe another demigod who is envious of Percy's powers or his popularity among their peers. This friend might see an opportunity to get Percy out of the way and so betrays him.
His water - controlling powers are super useful. He can use them to speed up the building process. For example, he can manipulate water to move heavy logs or metal parts more easily, like a natural crane. Also, if there are any problems with the ships at sea, he can use his powers to patch up holes or stabilize the vessels in rough waters.
In 'percy joins the romans fanfiction', it could start with Percy being transported to the Roman world by some magical or divine means. Once there, he has to adapt to their strict military - like structure. He might have conflicts with some of the Roman leaders who are skeptical of his loyalty. However, he overcomes these by showing his courage and loyalty to the greater good of the Roman demigods, and finally joins them in their battles against common enemies.