It could be a sleek, enchanted schooner. With sails that can change color according to the magical energy around it. The ship might have a figurehead that comes to life and gives advice, like a wise old wizard.
Maybe it's a small but very fast cutter. The hull could be made of a special magical wood that is resistant to dark magic attacks. It has hidden compartments where he can store his most precious magical items and potions.
It might be a large galleon - like ship. With multiple decks and rooms filled with all sorts of magical mechanisms. There could be a room on board where he practices his most powerful spells, and the ship itself could be powered by a combination of magic and the wind.
It could be a magical sailing ship. Maybe it has enchanted sails that can catch the wind of magic and sail across different magical realms. Or it could be a small, personal ship that he uses to explore hidden corners of Hogwarts lake.
He could have adventures like exploring uncharted magical islands. Maybe he'd encounter new magical creatures and have to use his wizarding skills to either befriend or fend them off. For example, he might come across a group of mermaids who guard a powerful magical artifact on an island.
Harry Potter could own custom-made wands or enchanted jewelry in fanfics. Also, some stories give him secret diaries or ancient magical tomes with hidden knowledge.
Well, in such a fanfic, Harry Potter might find himself in a world where ship girls exist. He could use his knowledge of magic to protect the ship girls from threats. For example, he could cast protective spells around their ships. Also, he might learn about the unique cultures and technologies related to the ship girls, and perhaps even introduce some of his wizarding world elements to them, like using magic to repair their ships faster.
In the 'Harry is the pet of someone' fanfiction, the owner of Harry could be a variety of people. It could be a young child who has always wanted a pet and finally gets Harry. This child would be full of excitement and love for their new pet. Or it could be an older person, perhaps a retiree, who has time to spend with Harry and enjoys the simple pleasures of having a pet around. Another possibility is that the owner is a magical being in a fantasy - themed fanfiction, and they have chosen Harry as their pet for some special reason related to the magic in that world.
There's also a possibility that it's a Chinese Fireball. These dragons are very beautiful and powerful. In a fanfiction, the author might choose this type of dragon for Harry Potter to own because it would add an element of exoticism and grandeur to the story.
Redemption is also a theme. For example, in some fanfictions where Draco is a main part of a ship, his journey towards redemption while being in a relationship with another character is explored. It adds depth to the story and the relationship.
Harry Potter might create laws that protect the rights of house - elves and other magical creatures. For instance, he could make it illegal to enslave house - elves and ensure they have proper working conditions and fair wages if they choose to work. Also, he'd probably have laws regarding the proper use of magic in public. Maybe there would be restrictions on using dangerous or untested spells in crowded areas to prevent accidental harm to others.
In a fanfic where Harry Potter goes on a cruise ship, there are numerous possibilities. For starters, he could be on the ship as part of a mission for the wizarding world. Perhaps there are rumors of some ancient magical artifact hidden on the ship. He'd be walking around, trying to blend in with the muggles while using his magical skills subtly. He might even make some new friends among the crew or passengers. He could use magic to protect the ship from any potential threats, like a sudden storm that seems to have a magical origin. And he'd surely have some internal conflict about being away from the wizarding world he's so used to.
He would likely use Transfiguration magic. This would allow him to shape the raw materials into the form of a staff. He could also use Enchantment spells to give the staff special powers like the ability to repel dark magic or enhance his own spell - casting abilities.