When geologists set out years ago to examine signs of a major cosmic impact that occurred toward the end of the Pleistocene epoch, little did they know just how far-reaching the projected climatic effect would be.
www.sciencedaily.com
en.wikipedia.org
en.wikipedia.org
Start with those two links. There's lots more evidence where that came from, including the fact that there are structures to be found underneath the sea which shows that some of the previous flooding actually never went away and thus a permanently reshaped coastline was the outcome.
Not everything is meant to be taken literally. It's kind of hard to say "A comet which impacted halway around the earth resulted in a massive tidal wave" when you don't have recourse to either advanced astronomy nor a basic understanding of how celestial objects displace water when they hit the ocean.
That's because there are stories of it worldwide.