the Gibraltar area. Postwar investigators upgraded the rating from "G—No Damage" to "B—Probably Sunk", leading to an erroneous historical record that U-869 was sunk near Gibraltar. For many years this attack was assumed to have been her end. Discovery off U.S. coast In 1991, Bill Nagle, a former wreck diver and the captain of Seeker, learned about a wreck off New Jersey and decided to mount a diving expedition to the site. On 2 September 1991, an unidentified U-boat wreck was discovered 73 meters (240 feet) deep (a hazardous depth for standard scuba diving) off the coast of New Jersey. Nicknamed U-Who, the exact identity of the wreck was a matter of frequent debate, and initially the wreck was thought to be either or . The discoverers of U-Who, John Chatterton, Richie Kohler, and Kevin Brennan, continued to dive the wreck for the next several years. (Three divers, Steve Feldman, Chris Rouse and "Chrissy" Rouse, died exploring U-869.) Eventually, the team recovered a knife inscribed with "Horenburg", a crew member's name. However, they learned at the U-boat archives that U-869 was supposedly sent to Africa, so this piece of evidence was initially disregarded. A few years later, they found part of the UZO torpedo aiming device, and a spare parts box from the motor room engraved with serial and other identifying numbers. On 31 August 1997 they concluded that the boat they found was U-869. The location of the wreck is approximately . Cause of sinking The men who found U-869 believed it was a victim of her own torpedo, which may have become a "circle-runner". Torpedoes manufactured later in the war had acoustical seeking capability. It was theorized that the torpedo was initially fired in a turning pattern and when it missed her target, it picked up the sound of the submarine's propeller. At least two other German U-boats supposedly have been lost due to their own torpedoes: in 1944 and in late 1943. Chatterton and Kohler based their theory largely on a lack of evidence to support other causes for sinking. They claimed there was no reported naval activity in the vicinity, thereby ruling out a sinking by attack. Moreover, the damage to the hull was from the outside and thereby ruled out an internal explosion. This problem also affected the US submarine force at least twice, as seen with and . Gary Gentile, a noted wreck diver,