Imagine this scenario. It is almost two millennia ago. You live in a beautiful, seaside city. The surrounding land is flat and fertile. Water is abundant. As a bonus, your city sits beside a deep water harbor and enjoys the benefits of foreign trade. Your lovely city is called Bathonia.
Farther along the coast, there is another location. Water is scarce. There are steep hills overlooking another deep water harbor. Trade is possible, but the lack of water is a serious handicap. Food has to be grown elsewhere. This location came to be called Constantinople.
For some reason not fully understood, about two millennia ago, the population abandoned Bathonia and built up Constantinople. Why?
One scenario posits that Constantinople was easy to defend from the Roman legions and other attackers. This makes perfect sense. The history of the Crusades proves the defensibility of Constantinople.
But what if something else were true? Some of the ruins of Bathonia are now submerged in a lake, cut off from the Sea of Marmara. What if a devastating earthquake suddenly closed the entrance to Bathonia’s deep-sea harbor? This, too, would make perfect sense. A natural disaster devastating a hometown is a good reason to pull up stakes and rebuild elsewhere.
Studies of Bathonian ruins made accessible by a drought that lowered the water level may shed light on why Bathonia was abandoned in favor of Constantinople, now called Istanbul.
But what about Yonaguni? Where did everyone go? Why did they leave? It is so much harder to find answers when your study target is at the bottom of the sea, scoured by fast moving ocean currents.