As shipwrecks of World War II continue to erode in the sea, their toxic cargoes continue to pose a catastrophic threat. Now, experts use cutting-edge tech to investigate and reveal the potential impact of these noxious underwater dangers. Examined are: Operation Davy Jones' Locker: the Allied post-war sea disposal of captured German chemical weapons; the SS Richard Montgomery, a Liberty ship sunk in the Thames Estuary, near Sheerness, England with 1,500 tons of explosives; and the Norwegian SS Skytteren scuttled off Måseskär, Sweden with 170 tons of oil on board. 

For over a century, the stories and wrecks of HMS Hampshire off the Orkney Islands and HMS Vanguard in Scapa Flow continue to be shrouded in mystery; two research teams are granted special access to investigate and uncover what happened to these WWI warships in their final moments.

Three historical collisions expose the volatile risks at sea and how they have shaped today's technological advancements. The RMS Queen Mary sliced through her WWII escorting light cruiser HMS Curacoa which sank in 1942 off Ireland's northern coast. An unidentified ocean-going schooner struck the passenger liner SS Oregon sinking off the New York coast in 1886. The SS City of Chester sank after the RMS Oceanic rammed her in 1888 in San Francisco Bay near the Golden Gate. Now, maritime researchers explore the remnants of these shipwrecks to uncover what happened in their fatal, final moments.

Experts investigate two of the greatest failed invasions in naval warfare history. Explore three wooden shipwrecks of the Spanish Armada (1588) in Streedagh Bay on Ireland's western coast and the battleships HMS Irresistible and Bouvet (French) sunk in the WWI Allied Dardanelles Campaign against Turkey in 1915.  

More than 50 massive warships of the German High Seas Fleet were scuttled in a matter of hours in the Scottish natural harbor of Scapa Flow during WWI. Thirty-eight were later salvaged. Now, marine archaeologists use cutting-edge tech to explore one of the greatest acts of defiance in wartime history. 

The aerial bombardment of the Japanese fleet at Truk Lagoon sinking 40+ ships and the Soviet torpedo strike of the German ocean liner MV Wilhelm Gustloff in the Baltic Sea killing 9,000 passengers are two of the most shocking attacks of WWII; now, expert divers explore these underwater graveyards for new evidence of these maritime conflicts.

The USS Arizona and the HMS Hood were two of the most powerful warships in history, but their weaknesses paid a fatal price; experts investigate evidence that may reveal why the age of the battleship has come to a sudden and violent end. Also studied are Bismarck, HMS Prince of Wales, and Yamato. 

The wreckages of three German U-boats are eroding at the bottom of the sea, along with the stories behind their disastrous fate. They are: UC-66, the only U-boat sunk solely by an Allied airplane in WWI off the Isles of Scilly; U-87, rammed by a British patrol boat in the Irish Sea during WWI; and U-480, sunk by a mine in the English Channel during WWII. (To counter Allied sonar, U-480 was coated with a rubber shield codenamed Alberich.) Now, a team of maritime archaeologists race to locate the submarines and solve the mystery behind their deadly demise. 

The enigmatic shipwrecks of SS El Faro and the RMS Empress of Ireland occurred a century apart, and both remain a mystery of the sea; armed with the latest technology, experts explore these doomed ships to discover what set them on the path to catastrophe.

The remains of five warships could reveal new insights into how the nuclear arms race changed the world forever; using 3-D sonar scan technology, an expert team of marine scientists investigates the catastrophic effects of atomic explosions at sea.