Tow Torpedo's also known as Tether Torpedos were Mines that were towed by Submarines into the hulls of Union Ships during the Events of the American Civil War, the usefulness of Tow Torpedos ended after the sinking of the USS Housatonic in 1864 by CSS Hunley that was armed with a Spar Torpedo. The sinking of 1964 changed the history of Navel warfare forever bringing about the beginning of Submarine Warfare.
During the American Civil War, the term torpedo was used for what is today called a contact mine, floating on or below the water surface using an air-filled demijohn or similar flotation device. (As self-propelled torpedoes were developed the tethered variety became known as stationary torpedoes and later mines.) Several types of naval "torpedo" were developed and deployed, most often by the Confederates, who faced a severe disadvantage in more traditional warfare methods. In this period, "torpedoes" floated freely on the surface or were bottom-moored just below the surface. They were detonated when struck by a ship, or after a set time, but were unreliable. These could be as much a danger to Confederate as to Union shipping, and were sometimes marked with flags that could be removed if Union attack was deemed imminent. Rivers mined with Confederate torpedoes were often cleared by Unionists placing captured Confederate soldiers with knowledge of the torpedoes' location in small boats ahead of the main fleet.
"Torpedoes" (mines) could also be detonated electrically by an operator on shore (as demonstrated also by Fulton), so friendly vessels or low-value enemy vessels could be ignored while waiting for the capital ships to sail over them. However, the Confederacy was plagued by a chronic shortage of materials including platinum and copper wire and acid for batteries, and the wires had a tendency to break. Electricity was a new technology, and the limitations of direct current for effective distance was poorly understood, so failures were also possible because of the decrease in voltage when the torpedoes were too far from the batteries. Former United States Navy Commander Matthew Maury, who served as a commander in the Confederate Navy, worked on the development of an underwater electrical mine.
On 12 December 1862, while clearing mines from the river preparatory to the attack on Haines Bluff, Mississippi, USS Cairo struck a torpedo detonated by volunteers hidden behind the river bank and sank in 12 minutes; there were no casualties. Cairo became the first armored warship sunk by an electrically detonated mine. It was raised in 1964, reconstructed, and is currently on display at the Vicksburg National Military Park
Union Navy Rear Admiral David Farragut encountered tethered and floating contact mines in 1864 at the American Civil War Battle of Mobile Bay. After his leading ironclad, USS Tecumseh, was sunk by a tethered contact mine (torpedo), his vessels halted, afraid of hitting additional torpedoes. Inspiring his men to push forward, Farragut famously ordered, as usually paraphrased, "Damn the torpedoes, full speed ahead!"