Not as he says it. The Pillars of Hercules are the Straits of Gibraltar and by Plato they are fine. I've read and reread it. He tells it in two books and there's no way around it. He means that the entire Atlantic ocean is shallow and full of mud and that nobody can cross it. You could sail around Europe or Africa (and people did), but cross it? No way. The sinking of Atlantis is the most famous part of the story, but it's (in Plato's account) a blatant untruth.
I do think a great land did sink, but not Atlantis. I think it was part of Western India which, thousands of years ago, suffered a huge geological upheaval and actually did sink into the sea. There was an expedition to find evidence on the sea bed, but the people who did it where idiots and dredged the sea bed instead of diving, ruining the site and all evidence. I do think it's the source of all the flood legends of the middle east and Europe though.
And I would've gotten away with it if it wasn't for those meddling kids!