Scientific American Frontiers on PBS

This look at mysteries of the deep traces the history (and the recovery) of the Civil War submarine Hunley, and profiles geologist and underwater explorer Bob Ballard, who found the Titanic in 1985. First up: The Hunley, a Confederate “torpedo boat” that sank off Cape Hatteras, N.C., in 1864. As for Ballard, he has been exploring in submersibles since 1964 but now favors unmanned, camera-laden craft. He also discovered hypothermal vents off the Galapagos Islands in 1977, and is now interested in ancient shipwrecks. “There's more history in the deep sea,” he says, “than in all the museums of the world.”