c) A hand-cranked submarine

During the Siege of Charleston, the Confederacy experimented with an innovative but ultimately unsuccessful military technology: a hand-cranked submarine. The most famous of these was the H.L. Hunley, which became the first combat submarine to sink an enemy warship. However, the Hunley itself was lost shortly after its successful attack. The use of such submarines was a groundbreaking development in naval warfare, reflecting the Confederacy’s efforts to overcome the Union’s naval superiority through technological innovation.