Many people have heard of the Hunley, the experimental Confederate submarine that sank the USS Housatonic in a daring nighttime operation. Less well known, however, is that the Hunley was not alone under the waters of America during the Civil War. Both the Union and Confederacy built a wide and incredible array of vessels that could maneuver underwater, and many were put to use patrolling enemy waters. In Submarine Warfare in the Civil War, Mark Ragan,...