In POTC (Pirates of the Caribbean) fanfic, 'Crossing the Bar' could potentially refer to a significant event or journey. It might be a metaphorical crossing of a boundary, like the characters leaving the safety of the known world (the bar could represent a sort of border in the sea). For example, it could be about the pirates sailing into uncharted and dangerous waters, facing new challenges and foes.
One idea could be that the One Ring somehow ends up in the world of Pirates of the Caribbean. Jack Sparrow, being the wily character he is, gets wind of its power and decides to either use it for his own gain or sell it to the highest bidder. The Fellowship, in turn, has to track it down in this strange new world full of pirates, sea monsters, and cursed treasures.
Definitely Legolas and Will Turner. Legolas with his amazing archery skills could teach Will some new techniques, and Will could show Legolas the ropes of being a pirate. They both have a sense of honor and loyalty, so they would make an interesting duo.
One main theme is the idea of karma or retribution. Since Barbossa was a pirate, his actions had consequences, and the ghost stories might show how the bad things he did came back to haunt him. For example, if he stole from someone, the victim's ghost might seek revenge in the stories.
The 'Crossing the Bar' may also be related to the theme of mortality. In pirate lore, the sea can be a very unforgiving place. Crossing a certain 'bar' could be seen as a step closer to death or a test of one's mortality. It could be a moment where the characters are forced to confront their own mortality and the fragility of their pirate lives.
Well, there are potc fanfictions that center around Davy Jones' backstory in more detail. Maybe showing his life before he became the feared sea creature. Some fanfictions also create new characters and their interactions with the existing ones. For example, a new pirate who challenges Jack Sparrow's status. And there are those that rewrite the ending of the movies, giving a different fate to the main characters.
Well, for potc fanfic, you could write about a new crew member joining Jack Sparrow's ship. This new character could have a special power, like being able to control the wind. They could use this power to help the ship escape from dangerous situations. Also, a fanfic about the origin of the Black Pearl would be cool. It could be that the ship was built from a cursed forest, and that's why it has some strange powers. Or you could write a fanfic where Davy Jones and Jack Sparrow team up against a new common enemy, like a powerful sea witch who wants to rule the ocean.
The 'A Study in Scarlet' PotC fanfic could blend the detective elements of the first story with the adventure and swashbuckling of PotC. It might have familiar faces from both in unexpected situations, making for an exciting read.
Another theme is redemption. Sometimes their relationship is a journey of one or both of them finding redemption in the eyes of the other. For example, Barbossa might see Jack in a new light and vice versa. It often plays out against the backdrop of their pirate adventures. And their relationship can also be about mutual survival. When facing dangerous situations like sea monsters or other pirates, they have to rely on each other's skills, which then deepens their connection.
One interesting Hector Barbossa fanfiction could be one where he teams up with a young pirate who is new to the seas. They embark on a journey to find a hidden treasure that Barbossa has only heard rumors about. It shows his mentoring side.