The H.L. Hunley was a human-powered Confederate submarine, launched in 1863. It was the first combat submarine to sink a warship. Sunk multiple times, after sitting on the seabed for over a century, it is now the subject of an extraordinary conservation effort to carefully preserve this icon of naval history. A painting of it:
Similar to how the ill-fated Apollo I lunar landing craft killed all three of its crew members, the H.L. Hunley was a costly technological advance. First it sank in August of 1863, killing five crew members, and was raised and returned to service. Then it sank again in October of 1863, killing all eight crew members, including its inventor Horace Hunley. Again it was raised and returned to service.
In February of 1864, The Hunley sunk the USS Housatonic with a spar torpedo; this was the first ship to be sunk by a submarine. The Hunley was then lost at sea that night; she sank a third time, killing all eight of her third crew. The USS Housatonic:
Nobody knows what brought down the Hunley for the final time, but historians have a couple of theories. One states that a crewman on the Housatonic was able to fire a rifle round into one of the Hunley's viewing ports. The other possibility is that the Hunley was damaged because of its proximity to the Housatonic when its spar torpedo detonated.
The Hunley sat sunk on the seabed for over 130 years. It was located in 1995, raised in 2000, and is now on display at the Warren Lasch Conservation Center in North Charleston, South Carolina, as it undergoes extensive research and conservation efforts.
The Hunley conservation project:
There are two National Geographic videos featuring The Hunley, as well as a full-length film starring Armand Assante and Donald Sutherland. I haven't seen any of them, but they're all extremely well-reviewed on Amazon:
Raising the Hunley
Secret Weapon of the Confederacy
Sub's conservation begins today | Archives | postandcourier.com
Friends of the Hunley YouTube channel
Friends of the Hunley
Previously: Steam-powered submarine