You have said that Lemuria sank in three stages. Did Atlantis too?
Yes it did. At the end of each of the ice ages. But not in the same way Lemuria did.
Pieces of Lemuria sank in time, giving its inhabitants (like the Hopi and the Australian Aborigines) the opportunity to move to safer ground. But Atlantis was twice entirely submerged to reappear as a different landmass and at a slightly different location. (See Secrets of the Hidden Realms.) It was then called Atitlan, Land of the Serpent Priests. Before the final submerging of Atlantis, the serpent priests moved to the Yucatán in long canoes.
In the Atlantean language Atitlan means 'The Heavenly Serpent' or 'The Serpent From Heaven' — the Pleiades.