It began with a barrel-shaped submersible that patrolled New York Harbor during the American Revolutionary War. Since then, the submarine has evolved into a vital weapon of war. Dive in as we track its history, from the 1775 Turtle to the 1879 Resurgam to the mighty German U-boats and nuclear subs of today. Rare archival footage, visits to surviving decommissioned subs, and interviews with crewmembers help explain how these machines became such a powerful symbol of naval supremacy.