Until a few decades ago, the ocean depths were almost as mysterious and inaccessible as outer space. Oceans cover two-thirds of the earth's surface with an average depth of more than two miles -- yet humans had never ventured more than a few hundred feet below the waves. One of the great scientific and archaeological feats of our time has been finally to cast light on the "eternal darkness" of the deep sea. This is the story of that achievement, told...

A look at the disaster that shocked the world on May 7, 1915, when the state-of-the-art ocean liner sank after being struck by a German U-Boat torpedo that killed over 1100 passengers.