Deep Sea Detectives - Season 2 Episode 14 The Confederacy's Secret Weapon

It was the first submarine ever to sink an enemy ship, but after only one successful mission the H.L. Hunley vanished with its crew and lay hidden for more than a century. The circumstances surrounding the disappearance of the Confederacy’s secret weapon have remained an enduring mystery since the Civil War era, but now NGC has uncovered what may have brought it down.