It's World War II and 4 allied ships are destroyed off the coast of southern England. Survivors had no idea what had hit them. Today, divers discover a sunken submarine, whose design and features are unlike anything seen before.

June, 1915. The S.S. Armenian is headed for England from the United States. She is carrying over 1400 mules for the battlefields of Europe. A German U-boat sinks her, and the outrage rings loudly from the American people.

An extreme dive reveals the mysteries of the 2nd World War British warship HMS Curacoa, rammed and sunk by the most famous liner in the world, the Queen Mary.

Within sight of the coast of France lies a sunken allied troop ship. Remnants of the 2nd world wreck scatter the sea bed, evidence of a forgotten tragedy. Nearly 800 American soldiers lost their lives, the event surrounded by secrecy and mystery.

Off the northern coast of Ireland, a massive shipwreck has laid unseen for decades. Now that divers are finally able to reach her, they can uncover the secret of how the HMS Audacious met her bitter end in World War I.