The Atlantic Sea is a geographical term that in the context of Atlantis studies is not to be confused with what we call the Atlantic Ocean. For the ancient Greeks ‘Okeanos’ was the name of a river that flowed around the known world.
Plato never referred to Atlantis being located in the Atlantic Ocean, instead he placed it in the Atlantic Sea. The first English translation of the Atlantis texts by Thomas Taylor at the beginning of the 19th century correctly translated the word as ‘Sea’, however, after that, most English translations used ‘Ocean’ including the most widely available offering from Benjamin Jowett.
This claim of mistranslation is supported by Plato who noted that “in those days the Atlantic was navigable” (Tim. 24e), which clearly implies that in Plato’s time it was not. Additionally, Aristotle seemed to echo Plato when he wrote(a) that “outside the pillars of Heracles the sea is shallow owing to the mud, but calm, for it lies in a hollow.” This is not a description of the Atlantic that we know, which is not shallow, calm or lying in a hollow and which he also refers to as a sea, not an ocean. Both seem to be describing relatively a small body of water. So, what sea were they referring to? The most popular suggestions so far are (1) The Western Basin of the Mediterranean, (2) The Tyrrhenian Sea or (3) The chotts of N.W. Africa.
Among others, Mário Saa a Portuguese writer identified the Western Mediterranean as Plato’s Atlantic Sea on a map in his book, Erridânia: geografia antiquíssima . A French website(b) supporting this identification has offered the map below. I also endorse this as the location of Plato’s Atlantic Sea.
(b) http://histoiresecrete.leforum.eu/t716-quelques-questions-se-poser-sur-le-Tim-e-Critias.htm (registration required)