In The Sea Hunters, his first nonfiction book, Cussler explores the special world of undersea adventure that inspired and has its fictional parallel in the Dirk Pitt novels. He describes his lifelong love for the sea and ships, and how his involvement with the search for John Paul Jones's famous Revolutionary War ship, the Bonhomme Richard, led to his establishing the NUMA (National Underwater and Marine Agency) Foundation, a nonprofit organization dedicated to the discovery and preservation of historic shipwrecks. From the more than sixty shipwrecks Cussler and his NUMA volunteers have found, he has chosen the twelve most interesting, whether because of the ship's history, the circumstances of its sinking, or the trouble, frustration, and peril that were encountered while trying to find the sunken wreck. With the same wonderful storytelling that Cussler brings to his novels, he describes his searches for such ships as the Union 24-gun frigate Cumberland, sunk during the Civil War by the Confederate ironclad CSS Virginia (formerly the Merrimack); the Confederate Hunley, which became the first submarine in history to sink a warship; the U-21, a German U-boat, which during World War I became the first sub to sink a warship and escape; and the American troop transport Leopoldville, which was destroyed by a German submarine on Christmas Eve, 1944, with huge loss of life; as well as Engine #51, the lost locomotive of Kiowa Creek, which roared off a storm-weakened high bridge in 1878. The wrecks date as far back as 1840 and span the continental United States, the Atlantic Ocean, and the North Sea.