On this day in the Civil War, a watchman on the USS Housatonic, a blockade ship patrolling in Charleston Harbor, sees something in the water making its way toward the ship, it turns out to be the Confederate semi-submersible ship H L Hunley.
The Hunley is armed with a torpedo, which blows a hole in the Housatonic on impact. Both vessels sink.
Charleston Harbor
The Civil War Book 