Basically what the title says; on a converted world, there is a jungle biome region where a pirate ship spawns inside, for some reason. If you use the seed this world uses and make a new world with it, going to the same spot generates a pirate ship, but in a proper ocean biome.

I guess structures that are biome-dependant don't exactly cater to new worlds using the biome blending feature?

Provided is a backup of the world generated by the game before I opened it in 1.18 Pre-Release 2, the world must've been last played on Release 1.2.4 since it was last played around March 2012. The world file is pre-conversion, meaning it can still be opened in 1.2.4.

Coordinates: 71, 77, 224

Seed: -63132140