The problem is, there hasn't been enough inquiry and research to decided either of those, and that's what needs to happen; of course, I don't think it will. I mean, these kinds of structures have been popping up all over the globe for decades, and nothing is being said of them.
But it's interesting isn't it that Plato thought there was an "atlantis." The Egyptians thought there was a "lost continent" called Mu. The Indians believed in Lemuria. I think there must be something to this.
Plato makes it clear where he supposes Atlantis to be which is past the Gibraltar Straights in the Atlantic Ocean. Scientists have checked the ocean and there is no such land mass. It is all formed from continents separating. Even the Azores are a result of volcanic deposit so they are not the peak of some former land as some writers have tried to suggest.
There is ample evidence to show that the ancients could navigate the sea much better than we give credit and that they knew the world was round (ancient maps have been found such as the Piri Reis, there is a Roman statue in Ephesus showing the emperor with his foot on a globe, tobacco traces have been found in Egypt...)
This would suggest that world communication can spread tales and lore. Many historians believe that the tale of Atlantis, the tale of Adam, the tale of Manu and Mu etc etc are all stories of a common source. Amongst native Americans they have similar tales of a flood myth. It did not have to be a total world flood to create such tales.
One thing we know for sure is that the ancients were clever people. It would make sense that a major environmental disaster would put the world into blackness and could be the reason for the fall of knowledge. Arguments as to what could have happened is a meteor hit the Earth, the moon was pulled into the Earth's gravity. Any of these would cause tidal wave, tide rises, major storms and earthquakes etc. It could even have put us into the ice age afterwards.