April 1940. When Hitler dispatches the U-Boat arm to protect troops invading Norway, a German submarine rushes towards the deep fjords leading to Narvik, the scene of two major deadly naval battles. While multiple encounters with British Royal Navy ships provide numerous targets, including the battleship HMS Warpsite, torpedo failures threaten their mission.

After a violent collision, an American submarine crew begins a desperate bid for survival.

American submarines risk everything to surface in enemy waters and rescue downed aviators.

It's January 1943 in the Pacific and American submarine skipper Dudley Morton is just 10 days into his first patrol aboard USS Wahoo. His mission: to sink Japanese ships and disrupt supply lines. This aggressive strategy is a radically new tactic for the U.S. Navy, and Morton is just the man to carry it out. See these water wars up close and witness Morton take on entire Japanese convoys above and below the Pacific in this thrilling exploration.

Submarine commander Dick O'Kane participated in the most successful attacks on Japanese ships during World War II, until his luck, and the last torpedo he fired, took a dramatic turn. We track O'Kane's successful career, first as a protege aboard the legendary USS Wahoo, and then as Commander of the short-lived but lethal USS Tang. Through expert testimony, we relive O'Kane's seminal triumphs, and the tragic path of his last warhead.

The USS Harder, led by Commander Sam Dealey, sank multiple Japanese destroyers, rescued Allied operatives from capture in Borneo, and outmatched many rival ships and aircraft to return home. And that was during just one patrol. Take a deep dive aboard this submarine as we relive this incredible war patrol in the spring of 1944, and witness the events that accelerated the campaign against the Japanese and earned Dealey the Medal of Honor.

The wolfpack tactic was made famous by Admiral Karl Donitz, Hitler's mastermind of submariners. His strategy: to send teams of U-boats to bear against the convoys of ships heading from Canada to Britain, cut maritime lifelines, and starve the enemy into defeat. Take a deep dive into the North Atlantic as we go above and below sea level to relive one of the first attacks of Donitz's lethal subs in 1940, headed by leader of the pack Commander Otto Kretschmer. Then follow Britain's war strategists as they race to combat this new deadly attack.

Just one month after the Japanese attack on Pearl Harbor, another enemy brought World War II to American shores, not through the air but beneath the sea. This is the story of Operation Drumbeat, German Admiral Karl Donitz's campaign to send U-boats to the doorstep of the U.S. and attack Allied merchant shipping from Newfoundland to North Carolina. Through archival war footage and military expert testimony, we reveal how the Nazis managed to hammer our coast again and again and why the U.S. Navy was unable to stop them.

A Nazi U-boat heading back for repairs unintentionally cruises right into the middle of a large Allied convoy on March 16, 1943. It is a lucky accident that sets the stage for the largest convoy battle of World War II. Relive this momentous chapter in the war for the Atlantic, an intense game of chess pitting Admiral Karl Donitz's wolf pack against a battered British Navy. It's a three-day showdown with unparalleled violence and unexpected outcomes that will turn the tide of the war.

Decorated American submarine commander Eugene Fluckey, determined to go out with a bang, defies expectations and returns to USS Barb for one last patrol. On the eastern coast of Northern Japan, Fluckey and his crew push the boundaries of submarine warfare to new limits by launching rockets from their sub and landing a crew of saboteurs on Japanese land in order to destroy a coastal rail line. It's a highly aggressive and ambitious patrol that will forever change the way subs are used in battle.

A German U-Boat Commander makes an unprecedented voyage to attack Allied shipping off the coast of Australia on Christmas morning.

The life of German U-Boat commander Fritz Julius Lemp, who accidentally sinks the passenger liner SS Athenia, takes a series of dramatic turns when he is later forced to the surface after attacking an Allied convoy.

In the icy waters off of Norway in 1945, a U-boat embarks on a mission to bring top-secret German technology to Japan, unaware that a Royal Navy V-class submarine has just been ordered to patrol the area. Neither commander manning their vessel realizes that they are about to face-off in the world's first underwater submarine dogfight. Witness the historic battle between HMS Venturer and U-864.

An American submarine commander risks everything in a fight from within an enemy convoy.

A German U-boat commander launches a shocking attack at the heart of the Royal Navy.

USS Silversides and its swashbuckling skipper, Creed Burlingame, saw their first action in the Pacific in May 1942. More than a dozen patrols later, the sub now rests in Muskegon, Michigan as a museum, an ongoing testament to its extraordinary history. Witness one of Silversides' most dramatic missions: aiding Marines in Guadalcanal by keeping Japanese reinforcements from reaching the island. It's an assignment fraught with depth charge attacks and aerial bombardments that nearly ended the mission and its crew.

German U-515 departs from France in 1944, bound for the African Gold Coast to hunt Allied ships. One thousand miles to the south, the U.S. Navy launches a new hunter-killer task force--a tactical combination of destroyers, escorts, carriers, and aircraft--to prevent German U-Boat resurgence. Witness the showdown between U-boat ace Werner Henke and U.S. Navy Bronze Star recipient Daniel Gallery and see how the unrelenting attack of hunter-killer groups changed how the Battle of the Atlantic was fought and won.

It was the most frightening moment of the Cold War: a crisis in Cuba in 1962 that brought the world to the brink of disaster. At the center of the drama are four Soviet submarines on a mission to supply nuclear torpedoes to bases on the communist island and the U.S. Navy hunter-killer group determined to turn the vessels around. Discover how grave miscommunications and fervent emotions could have led to catastrophe and the critical role played by the Second in Command aboard Soviet sub B-59.

It's 1941 and Erwin Rommel and his armies hope to take Egypt, gain control of the Suez Canal, and prevent Britain from receiving vital supplies from the colony of India and the Middle East. The Allies' last line of defense is a fleet of small, British U-class subs stationed on the tiny island of Malta. Despite unpredictable weather and a broken gyrocompass, HMS Upholder and its Lieutenant-Commander Malcolm Wanklyn battle to hold the line against the Axis powers and turn the tide of the North African Campaign.

The career of a bright, young U-Boat officer begins with promise when he is awarded command of his own submarine. But during their first two war patrols, clashes with the Executive Officer and Chief Engineer over Nazi ideology cause tension and outright conflict. The officers' complaints lead to Commander's court martial and the threat of execution.

A German U-Boat, desperately low on supplies and with the crew suffering from scurvy, must be re-fueled from a supply submarine to make it back to port. With Allied Hunter Killer groups tracking their every move, the U-Boat makes a desperate run for survival. When a destroyer closes in to ram, the enemy crew uses the opportunity to board and attack the American ship.

After an enemy attack forces an American submarine into a disastrous dive, the crew struggles to regain control while battling a deadly chemical fire that threatens their limited air supply.

October 1943. After their first war patrol ends in conflict and disappointment, a new submarine Commander must overcome dissent despite his unconventional choices for key roles. Under his leadership, the crew works together to build trust even as they travel to target enemy shipping in dangerous Japanese home waters.

In February 1945, an American submarine Commander receives an order to hunt Japanese submarines assigned to secretly evacuating VIPs from the Philippines. Their job to send fellow submariners to the ocean floor sparks a battle of tactics, stealth and risk that would set a record for the U.S. Navy in World War II.