When the area of the terrain gets loaded, they appear items that come from the bottom of the ocean, when inspecting you can find [underwater_ruin/big_warm_4] that has broken the natural generated terrain and is the cause for the floating items.
The structure itself also spawns almost floating

Steps to reproduce
-Create world with seed: -3510969334625325996
-Teleport to coords: 67.12 53.16 -201.80 1526.25 12.45