I could not agree more with you: this unknown civilization we are looking for was definitely a seafaring one. There is no doubt in my mind. Plato makes it clear, Hapgood makes it clear, and we now know that even the Neanderthals were crossing the seas hundreds of thoudands of years ago.
You might find it interesting that recent research has shown that areas close to the arctic had a better climate than they do today. More specifically, parts of Sibera, Alaska and Canada were ice-free.
Contrary to the simplified model scientists have in mind, it is apparent that human migrations are very complicated. People were migrating all the time and to all directions. DNA is a game-changer in this field but new evidence keeps popping up all the time and it is not easy being up to date.
There is only little DNA evidence presented in my book, so if you are mainly interested in that I suggest you look elsewhere. Other than that though, I think you would find my book interesting.
Thank you for sharing this very interesting information! I look forward to some great discussions this month!