Imagine a world that’s run on magic and steam. Fill it with a collection of races so different from each other that they might as well be alien species. Then picture a pirate fleet that takes every ship it captures and adds it to the collection of ships already bolted together into a miles-wide floating island.
What you end up with is a city-on-the-sea, one made entirely of steamboats and tall-ships and blockade-runners and pleasure yachts, all of which have been gutted and turned into libraries and markets and workshops and sports arenas, or just scraped down to the waterline and covered in soil to make farms. And around each corner is a woman with a scarab for a head, or a human with pistons instead of legs, or a cactus-man, or a priestess who used to serve as the figurehead for her ship, or any number of other people who were taken prisoner when their ship was pirated and are now trying to make a life for themselves as a citizen of the floating city.
And that’s only the setting. The story quickly moves on to a quest to find a hidden civilization, in order to recruit the one scientist who can track down and capture an impossible underwater creature big enough to pull the floating city to the literal end of the world: a fissure in the ocean (and the planet, and reality) known only as the Scar.