A United States Navy diver refers to a service personnel that may be a restricted fleet line (Engineering Duty) officer, civil engineer corps (CEC) officer, Medical Corps officer, or an enlisted (ND or HM rating) who is qualified in underwater diving and salvage. Navy divers serve with fleet diving detachments and in research and development. Some of the mission areas of the Navy diver include: marine salvage, harbor clearance, underwater ship husbandry and repair, submarine rescue, saturation diving, experimental diving, underwater construction and welding, as well as serving as technical experts to the Navy SEALs, Marine Corps, and Navy EOD diving commands. The U.S. Navy is the lead agency in military diving technology and training within the U.S. Department of Defense. The foundation of the Navy diving program consists of the Navy Diver (ND) rating for enlisted personnel who perform diving as their occupational specialty in the Navy. History through World War II The US Navy began employing divers in the middle of the 1800s; these were mostly were swimmers and skin divers using techniques that had not been altered for hundreds of years. Duties included the salvage and repair of ships, construction work and military operations, including the Battle of Mobile Bay during the American Civil War. Preparations for the battle included the sending of swimmers to clear mines from the path of Admiral Farragut's ships, that had been planted by Confederate States forces to prevent entrance to the bay. In 1898, Navy divers were briefly involved in an international crisis when the second-class armored battleship was sunk by a mysterious explosion while anchored in the harbor at Havana, Cuba. Navy divers were sent from Key West to study and report on the wreck. Although a Court of Inquiry was convened, the reason for the sinking was not found. As American technology expanded in the early 1900s the US Navy developed an interest in submarine warfare. However, throughout the period of 1912–1939, the development of the Navy's F-class, H-class and S-class submarines was marred by a series of accidents, collisions, and sinkings. As a result of these submarine disasters a corresponding growth in the Navy's diving capability was developed. Until 1912, US Navy divers rarely went below 60 FSW (feet of seawater). There is little documentation that the Navy had a diving program prior to 1912. In that year, Chief Gunner George D. Stillson set up a program to