Plato wrote about Atlantis sinking 9000 years earlier in 360BC, and how the Atlantic sea was still untraversable due to all the mud.
http://www.sacred-texts.com/cla/plato/critias.htm
The Emerald Tablets of Thoth also reference Atlantis.
And what is your theory on why the Atlantic was covered in mud and impassable? There are more than one historical documents from that time that mention it.