The USS Housatonic was in the blockading fleet at Charleston SC harbor. The officer of the deck sighted an object in the water 100 yards off, approaching the ship. "It had the appearance of a plank moving in the water," he later reported. All hands were called to quarters, it was too late.
The CSS Hunley became the fist submarine in history to sink an enemy warship. The Housatonic sank to the bottom of Charleston harbor in 5 minutes.