Broken Single Biome: When selecting any Deep Ocean biome (Lukewarm, Cold, Frozen, etc.) it generates like a single cave biome, and there's no ocean, asides from the Aquifers.

Bugged Ocean Structures: This seems to be a 1.18 bug, where shipwrecks would generate above water, and ocean ruins would as well, the biggest (literally) structure that bugged was the Ocean Monument, where it would generate a giant box of water in the ground and place some sea grass and kelp around (it would even happen underground too!)

Here's some pictures

(I'll have to make a follow up because I ran out of space to put more pictures in, which will come soon)