The Navy suffered its worst peacetime disaster on April 9, when the nuclear attack submarine Thresher sank off the New Hampshire coast during routine sea trials. Diving to a thousand feet, the sub developed a small leak in her hull. The leak triggered a short circuit, shutting down the submarine’s nuclear reactor. Powerless and unable to blow her ballast tanks, the Thresher plunged into an eighty-four-hundred-foot ocean abyss called the Wilkenson Deep. Mounting pressure crushed her hull, killing all 129 crew members.