She was built in 1863-4 at Mobile by Mr. Horace L. Hundley, at his own expense. She was made of boiler plate, was shaped like a fish twenty-four feet long, five feet deep, three feet wide; she had fins on each side, raised or depressed from the interior; her motive power was a small propeller worked by manual power of her crew seated on each side of the shaft; she was provided with tanks which could be filled or empitied of water to increase or dimish her displacement; but had no provision for air storage. The captain stood in a circular hatchway well forward and steered the boat, and regulated the depth at which she should proceed. When she dived all was made tight until she rose again. She had no ventilation. She was designed to tow a torpedo astern, dive under the vessel attacked, dragging the torpedo after; she would then rise to the surface on the other side, when the torpedo would explode by contact with the bottom of the vessel, and the torpedo boat make off in the darkness and confusion. General Maury states that on her trial trip, which he saw, she towed a floating torpedo, dived under a ship, dragging the torpedo, which fairly exploded under the ship's bottom, and blew the fragments one hundred feet into the air; and that not being able to use her in Mobile, he sent her, and her crew to Charleston. It is said that during another trial in Mobile she sank and all on board perished before she was raised. Lieutenant Payne, of the Navy, volunteers to take her out, and secured a volunteer crew of sailors. She was named the "H. L. Hundley." While tied to the wharf at Fort Johnston, whence it was to start at night to make the attack, a steamer passing close by, filled and sank it, drowning all hands save Payne, who was at the time standing in one of the manholes. She was promptly raised, but was again sunk, this time at Fort Sumter wharf, when six men were drowned, Payne and two others escaping. When she was brought to the surface again. McKinley and a trained crew came from Mobile, bringing with him Lieutenant Dixon, of the Twenty-first Alabama Infantry, to fight the boat. He made repeated descents in the harbour, diving under the receiving ship again and again successfully. But one day, when Dixon was absent from the city, Mr. Hundley, wishing to handle the boat himself, unfortunately made the attempt; it was readily submerged but did not rise again and all on board perished, from asphyxiation. When the boat was discovered, raised and opened the spectacle was indescribably ghastly, the unfortunate men were contorted into all kinds of attitudes horrible to see; some clutching candles, evidently endeavouring to force open the manholes; others lying on the bottom tightly grappled together; and the blackened faces of all presented the expression of their agony and despair.