What's the Story of the Atlantis Islands?

If these islands existed, definitely did. When would they have been around? If they survived long enough to be on these maps, you know, they'd have to have been around in the early, early middle ages. And so how did they end up underwater then? Was there a kind of massive natural disaster like the Atlantis story? I mean normal coastal erosion processes and we find this all around the coast of Britain.