I was listening to the Fall of Civilizations podcast and one ep was talking about the huge areas that were covered by water post-Mini Ice Age and how rapidly that change occurred. I’ll get the numbers wrong, so I won’t try to quote it, but it was shocking. It made complete sense that people migrating from that area to higher ground would perceive the entire world flooding.
I believe this was around the time of the Sumerian culture, which gave us The Epic of Gilgamesh and the first flood. Very interesting stuff. Can’t recall if it was the ep on Sumer or Assyria or another, as they often have a lot of overlapping events told from the point of view of the culture in question.