During the First World War, two powerful warships, HMS Hampshire and HMS Vanguard, sank in controversial circumstances off the island of Orkney – north of Scotland. Following permission from British military authorities to dive these official war graves, we can now bring two very important and deeply mysterious wreck stories to public attention.

Thousands of WW2 wrecks lay dormant in the world’s waters. 75 years later, the relentless power of the ocean has eroded these once proud vessels to the brink of total collapse. In this episode we discover two ships laden with deadly toxic cargos. The sunken beasts are like ticking time bombs and no one knows exactly when or how they might explode.

Collisions at sea are of the most costly accidents, both financially and to lives. Exploring 3 historical wrecks – HMS Curacoa, SS City of Chester, and SS Oregon – poignantly demonstrate the devastation. CGI recreates their events, while historian and archaeologist investigations reveal the major risks and causes across the globe, including how evolving technology and regulations have curbed this.

In the wake of WWI, 74 of the most powerful warships of the German High Seas fleet disappear into the depths of Scapa Flow. We follow maritime archaeologists and historians on an investigation to interrogate the motives, actions, and outcome of the greatest scuttle and act of defiance in wartime history. Witness testimony and CGI brings to life both the scuttle and 20th century salvage operations.

The stories of two of the greatest failed invasions in the history of naval warfare. In 1588 King Philip II of Spain assembled his Armada to sail to England and overthrow Queen Elizabeth I. Centuries later, the Allies make massive military miscalculations when their fleet is crushed by Turkish artillery in the Dardanelles. Questions remain around the dramatic sinking of French battleship Bouvet.

This episode tells the stories of two shocking revenge attacks in WW2. In 1944, in retaliation for Pearl Harbor, the Americans launched a massive aerial bombardment of the Japanese fleet in the Pacific - andin the Baltic; the most shocking attack in Maritime history. The German liner Wilhelm Gustloff was torpedoed by a Russian submarine, with the loss of some 10,000 people.

We uncover the remains of warships from the remote Pacific to the deep Atlantic revealing new insights into how the atom bomb changed our world forever. In the Pacific a marine science team conduct the first ever 3D sonar scan of ships sunk in nuclear blasts in 1946. Examination of their wrecks and witness testimony now provide new insights into the terrifying effects of the atomic explosions.

Survivors' stories and world-leading shipwreck investigators uncover how the most powerful warships in history had their weaknesses and paid a fatal price. We witness the catastrophic damage on HMS Hood in one of the deadliest naval engagements in history. The story of the USS Arizona at Pearl Harbor shows us how vulnerable a heavily-armoured battleship could be – now a war grave for over 1100 men.