Ice Age melt down
This is old news as it has long been speculated that the origin of Sumaria and other ancient places lay out there under the Gulf waters.
It must have an incredibly fertile place with a mild and stable climate for all the millenia of the last Ice Age. No wonder we have legends of a perfect place in our folk memory. It certainly fits the bill for the Garden of Eden.
I surmise that the ending of the last Ice Age was not a gentle drip by drip affair, but rather a number of catastrophic ice sheet collapses. Low lying land caught by a one or two metre sea level rise would soon disappear under the waves. An ice sheet collapse would probably trigger major climatic events to go along with sudden sea level rise.
These events would have been extremely stressful to cultures used to millenia of peace and plenty. Hardly surprising that we should have ancient memories, as legend and myth, of drastic events like expulsion from perfect places and Flood Myths.
When remains of ancient cultures are found beneath these waves, perhaps people will have more respect for our ancient legends and myths. These were probably eye-witness accounts of events far more disastrous than our present global warming scares.