True, but aquatic catastrophes have got to be the least suspected. Nobody expects a local flood to result in the extinction of an entire species.
The Toba supervolcano eruption of approx. 75,000 years ago is a suspect in causing a bottleneck in human genetics, where maybe only a few thousand humans were left alive in the world. The eruption would likely have disrupted normal weather patterns. The tectonic activity could well have caused tsunamis.
Heavy rain and flooding anybody?
75,000 years would be a extremely long time to pass down an oral tradition. But something that major... who knows?