"Artifacts at the site are clearly well preserved, with carved wooden beams, wooden branches and stone tools," lead researcher Robert Ballard said.
"We realize the broad significance the discovery has and we're going to do our best to learn more," Ballard said in a telephone interview Tuesday from his ship off the northern coast of Turkey, west of the community of Sinop.
Fredrik Hiebert of the University of Pennsylvania, the team's chief archaeologist, said the discovery "represents the first concrete evidence for occupation of the Black Sea coast prior to its flooding.
"This is a major discovery that will begin to rewrite the history of the cultures in this key area between Europe, Asia and the ancient Middle East," Hiebert said.
The remnants of human habitation were found in more than 300 feet of water about 12 miles off the coast of Turkey.
Many ancient Middle Eastern cultures have legends of a great flood, including the Bible story of Noah.
Columbia University researchers William Ryan and Walter Pittman speculated in their 1997 book Noah's Flood that when the European glaciers melted, about 7,000 years ago, the Mediterranean Sea overflowed into what was then a smaller freshwater lake to create the Black Sea.
Last year Ballard found indications of an ancient coastline miles out from the current Black Sea coast. The new discovery provides evidence that people once lived in that now inundated region.
Ballard, a National Geographic Society explorer-in-residence, said he studied shells found along the ancient coastline and found two types. One group is an extinct type of freshwater shell, while the second is from saltwater shellfish.
The saltwater shells date from the present back 6,500 years, while the freshwater shells all date to 7,000 years ago and older.
"So we know that there was a sudden and dramatic change from a freshwater lake to a saltwater sea 7,000 years ago," he said Tuesday.
"And we know that as a result of that flood a vast amount of land went under water.
"And we now know that that land was inhabited. What we don't know is who these people are, we don't know how broad their settlements were ... but we're expanding our studies to try to determine that."
Ballard said his team, using remote-controlled underwater vessels with cameras, located a former river valley beneath the sea, and in the valley was the collapsed structure. Remains include preserved wooden beams that were worked by hand.
The structure was "clearly built by humans," and was characteristic of stone-age structures built 7,000 years ago in the interior of Turkey, Ballard said. It contained a stone chisel and two other stone tools with holes drillethrough them, he said.
Nothing has been removed from the site. "When you first find a site you don't just run in there and start picking up things," he said.
The group is now mapping the site and looking for other structures in the area.
"This is a work in progress," Ballard said. "It is critical to know the exact era of the people who lived there, and to that end we hope to recover artifacts and wood for carbon dating so we can figure out what sort of people lived there and the nature of their tools."
The discovery occurred within coastal waters of Turkey, whose Directorate of Monuments and Museums has a representative on the research vessel.
Ballard, best known for finding the remains of the ships Titanic, Bismarck and Yorktown, among other discoveries, operates the Institute for Exploration in Mystic, Conn.
His expedition is sponsored by the National Geographic Society, which is planning a book and television programs on Ballard's Black Sea research.