A longstanding mystery surrounding a Confederate submarine which sank during the Civil War appears to have been solved.
The pioneering vessel, dubbed the H.L Hunley, is credited as the first submarine to successfully down an enemy ship, but that historic moment now appears to have been the cause of its demise.
While out at sea in 1864, the Hunley attacked and sunk the U.S.S. Housatonic and then promptly vanished shortly thereafter.
Incredibly, the submarine was not seen again for another 131 years, when the vessel was found intact on the seafloor off the coast of South Carolina in 1995.
After the famed craft was raised from the water in 2000, it was donated to the state of South Carolina for historic preservation and study.
In the ensuing years, researchers have examined both the vessel and the bodies of the crew inside of the craft in an attempt to discern what may have caused it to sink and experts now believe they know the answer.
A recently-published report concludes that the downing of the submarine was caused by a blast wave created by the vessel's own rudimentary torpedo system backfiring.
According to this scenario, an enormous wave of pressure swept through the cabin of the submarine when it struck the Housatonic.
The powerful blast would have been enough to render the crew of the submarine either knocked out or incapacitated and subsequently led to the sinking of the vessel.
This, researchers believe, is why the bodies of the crew give no indication that they were trying to escape the submarine nor react to damage to the ship that was causing it to sink.
Considering how horrifying it might be to die in a sinking submarine, it is somewhat comforting that the crew were probably unaware of their impending doom and passed rather peacefully while unconscious.