First Evidence of Humans in North America Found Off Florida, New Study Says
http://www.popularmechanics.com/science/a20872/tools-mastodon-florida-underwater-archaeology/It took decades, and a countless number of SCUBA tanks. Now, the painstaking excavation of an underwater archaeological site in northern Florida may change our understanding of when humans first populated North America.
A team of archaeologists led by Jessi Halligan—an anthropologist who specializes in underwater archaeology at Florida State University—just completed an aquatic dig of the oldest archaeological site in the American Southeast. It's a deep sinkhole called the Page-Ladson Archaeological Site located just beyond the southeastern skirts of Tallahassee in the Aucilla River. Halligan's team found stone knives and mastodon bones, tusks and dung, leading the scientists to believe the mastodon was either butchered or scavenged at the site by humans. Most interestingly, 71 individual radiocarbon dates show that the site is at least 14,550 years old—a full 1,500 years before many scientists recently believed humans first populated North America. The underwater dig was outlined today in the journal Science Advances...
There's some pretty cool info about how they did this at the link. Real Dirk Pitt kind of tech.