In 1991, professional diver John Chatterton discovered a sunken German U-boat from World War II, lying undetected only 60 miles off the New Jersey shore, its unexploded torpedoes and the bodies of its crew still aboard. This two-hour special follows Chatterton and his dive partners in their dangerous quest to identify the missing U-boat, a pursuit that takes six years and costs three lives. The U-boat's history involves unusual coincidences and a startling twist of fate.

An expedition looks into whether Titanic's hull had a construction design flaw that caused her to break apart. Featuring advanced CGI technology, archive documents and photographs, as well as footage from the modern-day History(R) expeditions, "Titanic's Achilles Heel" is a remarkable journey into the ongoing legacy of a ship that continues to capture the world's attention.