Ancient legends, even when based on real events, are often distorted beyond recognition by the retelling. I would be very leery of documentary evidence like the Bible or Plato and prefer instead to rely on archaeological investigations. This is especially the case where the ancient texts refer to incidents that occurred in pre-literate times.

Mesopotamia is flat and between two rivers, and very prone to flooding. A hydraulic civilization dependent on water control structures for agriculture would be very concerned about devastating floods and have a long memory for them, but their folklore would not be a very dependable source of historical data. I've often speculated that the Noah story wasn't about an Ark at all, but about a smart herdsman who simply moved his livestock onto high ground and survived a flood that wiped out all his neighbors. Legend and rumor did the rest.