Jovan Kesic came up with a brilliant study of Hapgood's 'Maps of the Ancient Sea Kings' – I have probably read the conclusions elsewhere but the subject matter goes back to the 1970s and 1980s and was completely ignored by mainstream. Hapgood wasn't one of them I suppose and had come out with outlandish ideas, in their minds eye, such as Pole Shift (a really no go subject in mainstream). In 'Maps of the Ancient Sea Kings' he thought ancient mariners had mapped the outline of Antarctica and showed it ice free. This had taxed the brains of some people at SIS way back in the 1980s but the subject has been shelved for a long time. Jovan resurrected it in reply to a query by somebody else and posted the link – http://archive.aramcoworld.com/issue/198001/piri.reis.and.the.hapgood.hy… … which is worth reading if you have forgotten about the subject or are labouring in the false belief people actually did visit an ice free Antarctic.
There was some speculation that in the Mid Holocene Warm Period (roughly 6000-3000BC) the coastline of the Antarctic might have been free of sea ice as in the Arctic, during the same period, it is thought that summer sea ice virtually disappeared most years as a result of a warmer global climate. However, the North Pole is in open sea whereas the South Pole is in the middle of a continent. Big difference. However, I suppose summer sea ice in the Southern Ocean could have meant the coast was free – but ancient mariners would still have been able to see the ice on the continent itself (but the big anomaly is that the maps do not display any hint of ice anywhere). Therefore one can understand why mainstream kept Hapgood at arm's length as in geochronology Antarctica has been covered in ice for millions of years. Not only that you would have to discover a maritime civilisation that was plying the oceans in the Mid Holocene period and as far as we know there were none (unless you bring Atlantis back into view). Basically, Hapgood had no evidence, apart from his interpretation of the maps, for his theory, which left him high and dry. In later life Hapgood is said to have sat back in the hope that something might be turned up by archaeologists – but this has not occurred. The link above is by an author that has taken it upon himself to do the work the academics failed to do – make sense of the maps. He seems to have done a pretty good job.
Somewhat later than Hapgood we had the Flem Ath's theory that Antarctica was Atlantis – using Hapgood's shifting poles by sliding crust to explain why it is now covered in ice. That idea never got anywhere either – but the authors sold a lot of books. I think I have probably got a copy somewhere (in the loft space I expect).
I leave you to read the conclusions and article in the link above.