Men have had the legend of Atlantis for many years now, and it has supposedly been found in several areas; but none have been proven to actually be the lost city of Atlantis. Amazingly, there seem to be many more of these underwater megaliths, stairways, and various other artifacts that were definitely part of some ancient civilization, and at a time when it was not covered by water. One of the theories about the earth is that it was once possibly just one large continent, and broke apart, maybe from the flood of Noah, maybe from earthquakes, or even a meteoroid strike. We will proabably never know that part for sure. Whatever happened, the megaliths have been found not only in the ocean; but also in some of the deeper, large lakes, like Lake Huron. Here is an interesting article about some of them, and it also has video of some of the underwater structures. http://thetruthwins.com/archives/an...ctures-found-on-the-bottom-of-the-ocean-floor
Here are a few more of the ideas, beliefs, and conspiracies relating to the Lost City of Atlantis, including an article that I wrote for Aviva Directory about one of them that involves the Nazis. Most of them, I don't give much credibility to, but it seems clear to me from the shape of our continents that they had once been connected. So I would imagine that if people were around at the time, there are probably quite a few former human habitations that are underwater now.
All this is fascinating. If we as a species manage to destroy ourselves, nature would eventually reclaim even our largest cities. Imagine a species ten thousand years from now excavating those areas.
At the ice maximum during the last ice age 18,000 years ago, sea levels were 400 feet lower than today because so much water was locked up in ice on land. So, yes many of remnants of earlier civilizations existed near seashore then as they do now. That was not the only ice age. The climate began cooling about 3.5 million years ago and scientist reckon there have been about 35 ice ages since then. The Milankovitch theory seems to explain this. Some ice ages were more severe than others. At any rate, the lower sea levels certainly explains how these megaliths can exist and it also explains how Asians entered America over the Beringa land bridge and traveled down the coastlines into more equitable climate zones. It must have been a good life for them beach combing their way to the southern lands, finding lots of shellfish on the shores and finding small game in the bordering woods as they proceeded southward. We can find no evidence of their nomadic existence because it's under 400 feet of water!