V 1.19.2, V2.0 Fabric

It feels like the ocean monument is in a hole in the ground.
Maybe if this happens you fill the air blocks with stone. Or just change the level of the ground.

This is intended, as otherwise they would protrude way too much from the surface.

I noticed it's much less noticeable if they generate in deep ocean type biomes, otherwise they do the hole thing in a normal ocean. Way you can "fix" it is set them to only generate in deep oceans I suppose since they have a lower surface on the ocean floor then a normal ocean giving the monuments more leeway to not look derpy compared to the surroundings