>> it probably was a bad day. and a lot of real estate, 150,000 square kilometers of land went under. >> and 400 feet below the surface, ballard believes he's found proof of that catastrophic event. >> and i love it. i love it. i love it. i love it. i love it. >> they unearthed an ancient shoreline. >> we have actually dated it about 5,000 b.c. >> and that is about the time that the bible says noah and the great flood happened. >> exactly. >> i mean, wow. >> so, it nailed it. >> ballard and other who is agree with the so-called black sea theory believe the survivors of this traumatic event passed the story down from generation to generation and eventually inspired the biblical account. >> here's the problem, when people read the story, they say, well did it cover the whole planet in water? no, but it covered their world. >> so, that explains the stories that were handed down. >> correct.