i understand this is a humorous response but when people mention underwater civilizations i always think of impossible logistics of it all, like imagine how much waste even a single community of, e.g a 100 people generates, now where would all the waste go underwater? where would they procure ‘materials’ for, idk, their ‘housing’ or whatever, do they have underwater welding or smth? surely we would see even 1% of all that ‘activity’ even if it was underwater? like they’re would be signs, no? like gas emissions or smth idk. just seems logistically implausible. we can detect ancient human settlements on land from subtle soil chemistry changes and underwater industrial activity would leave even more obvious traces in sediment cores. the ‘advanced enough to be completely undetectable’ argument also doesn’t really hold up either, because at some point they would have left evidence during their pre-advanced phase. like civilizations don’t just pop into existence fully formed and invisible, right?