The comet fragments that struck North America in 11,800 BC wiped out the megafauna, the Clovis culture, brought on the Younger Dryas - the coldest era on record. When the reformed Ice Cap melted sea level rose 300-700 feet worldwide causing the virtual overnight flooding of lands that were prime beaches, harbors, lowlands with cities, towns, villages an so on. And so the legends began. But the flood really happened.
You can perhaps understand the consternation of the multitudes who lived (and died) in the basin that is now the Mediterranean Sea, and then also those who lived in what is now the Black Sea.