You would be surprised how right you are.
During the last ice age, the water levels were much lower around the globe, and since humans like to live near water, it makes sense that our history, beyond the past 12k years or so, is under water.
It would also explain why every culture has a flood story.
http://news.nationalgeographic.com/news/pf/40939571.html
[heading] Archaeology: Undersea Adventures and Pre-Columbian Mingling
Eric Powell, a senior editor at Archaeology magazine, says some of 2009’s most exciting digs will be undersea.
“There is a lot of good work on everything from Bronze Age shipwrecks in the Aegean to Paleolithic archaeology,” he said.
“People are starting to think of underwater archaeology as focused not just on nautical history, but on the prehistoric landscape that existed when glaciers had water tied up and sea levels were much lower,” he said.
Powell expects new evidence of pre-Columbian mingling to shake-up the field as well.
“I think in the coming year you’re going to see some discoveries announced that shed light on the New World/Old World contacts before Columbus came,” Powell said.
“We may realize that there was much more contact than we previously thought.”