9 p.m. April 9, Nat Geo Dr. Bob Ballard has been living and breathing the Titanic since he was part of the team that discovered it in 1985. Now, he revisits the iconic ship in an entirely different way--from the perspective of those who set sail on it some 100 years ago. Ballard travels to the shipyards of Northern Ireland to meet with descendants of Titanic's Guarantee Group--nine men who helped build the magnificent ship with their own hands and were selected to sail on her maiden voyage. Throughout his journey, Ballard is driven by one personal question--ill the Titanic survive another 100 years? Already, crucial pieces of Titanic's history are gone, including the crow's nest where lookouts spotted the fatal iceberg--possibly knocked into a cargo hold by a passing tourist submarine. PHOTO: Bob Ballard explores the massive Thompson Dry Dock in Belfast, Northern Ireland. At the time of its construction, this was the largest dry dock in the world -- built especially for Titanic and her sister ships.