User blog comment:Sporekypig/Weird buildings theories?/@comment-2056021-20150405080632

I knew of and have been to the surface ruin, but I never heard anything about that underwater one.

Can someone give the coordinates or the rough location of it?

As for a theory to their existance: I think the devs are mainly just testing around what is possible and what not and how. They might have a very, very vague idea of a overlying plot, but judging from the Trello board I don't think they have a direct story concept. And even if, these specific ruins really seem very "debug-y".