It was hidden from discovery all this time by a single errant digit.
The mystery began on Jan. 28, 1944, when the Grayback, one of the most successful American submarines of World War II, sailed out of Pearl Harbor for its 10th combat patrol. By late March it was more than three weeks overdue to return, and the Navy listed the submarine as missing and presumed lost.
After the war, the Navy tried to piece together a comprehensive history of the 52 submarines it had lost. The history, issued in 1949, gave approximate locations of where each submarine had disappeared.
The Grayback was thought to have gone down in the open ocean 100 miles east-southeast of Okinawa. But the Navy had unknowingly relied on a flawed translation of Japanese war records that got one digit wrong in the latitude and longitude of the spot where the Grayback had probably met its end.
The error went undetected until last year, when an amateur researcher, Yutaka Iwasaki, was going through the wartime records of the Imperial Japanese Navy base at Sasebo. The files included daily reports received by radio from the naval air base at Naha, Okinawa — and the entry for Feb. 27, 1944, contained a promising lead.
The report for that day said that a Nakajima B5N carrier-based bomber had dropped a 500-pound bomb on a surfaced submarine, striking just aft of the conning tower. The sub exploded and sank immediately, and there were no survivors.
“In that radio record, there is a longitude and a latitude of the attack, very clearly,” Mr. Iwasaki said. And it did not match what was in the 1949 Navy history, not by a hundred miles.
Mr. Iwasaki is a systems engineer who lives in Kobe, Japan, and who became fascinated as a teenager with the Japanese merchant ships of World War II — four-fifths of which were sunk during the war, he said. Uncovering the history of those ships necessarily brought him into contact with records on submarines. “For me, finding U.S. submarines is part of my activity to introduce the tragic story of war,” he said. “It is my hobby, and also my passion.”
His work brought him to the attention of Tim Taylor, an undersea explorer who has set out to find the wrecks of every American submarine lost in the war. In 2010 he found his first submarine, the U.S.S. R-12, off Key West, Fla., where it sank during a training exercise in 1943. He set up the privately funded Lost 52 Project to track down the rest, relying on technology that had become available only in the last 10 to 15 years.
Mr. Taylor says that of the 52 lost American submarines, 47 are considered discoverable; the other five were run aground or destroyed in known locations.
Mr. Taylor and his wife, Christine Dennison, have been searching for those 47, and have begun to focus on the ones that were probably sunk near Japan.
Through his work in undersea exploration, Mr. Taylor was introduced to Don Walsh, a former Navy submariner who, as a lieutenant in 1960, reached the deepest point of any ocean on Earth, in the Mariana Trench near Guam. Mr. Walsh gave Mr. Taylor his copy of the 1949 Navy history, “U.S. Submarine Losses, World War II.”
Armed with the information in that book and Mr. Iwasaki’s discovery, Mr. Taylor and the Lost 52 team decided to make a run at finding the Grayback.
The Grayback’s last patrol was its third under the command of Lt. Cmdr. John A. Moore, who had been awarded the Navy Cross for each of the first two. His third Navy Cross would be awarded posthumously, after the submarine sent 21,594 tons of Japanese shipping to the bottom on its last mission. In all, the Grayback sank more than a dozen Japanese ships. The Navy considers submarines like the Grayback to be “still on patrol.”
Like Commander Moore did 75 years before, Mr. Taylor launched his mission to Okinawa this spring from Hawaii. When they reached Japanese waters in June, he and his team fought through mechanical and electrical problems that bedeviled their mission.
They were searching an area where the ocean was 1,400 feet deep, and their main search tool was a 14-foot-long autonomous underwater vehicle weighing thousands of pounds that Mr. Taylor likened to an underwater drone. It would dive to just a few hundred feet above the sea floor and then spend 24 hours pinging with different sonars back and forth across about 10 square nautical miles. When the drone returned to the mother ship, technicians downloaded its data, using computer software to stitch all of the sonar imagery into one coherent picture that they could quickly review.
“When you’re on these sites, you feel like you’re one breakdown away from having to go home,” Mr. Taylor said of the search area. “So every day is precious.”
On the next to last day of the expedition, the drone reported a malfunction one-third of the way through a planned 24-hour mission. As they recovered the drone, Mr. Taylor said, half of his crew started getting the ship ready to return to port, thinking that the vehicle was likely to be beyond quick repair. But Mr. Taylor began reviewing the images captured by the drone.
He quickly spotted two anomalies on the sea floor, and readied another of the ship’s remotely operated vehicles to visit the bottom. Unlike the drone, this one was steered manually from the mother ship, and had high-definition cameras.
In a matter of hours, Mr. Taylor was looking at the hull of the Grayback and, lying about 400 feet away, was the submarine’s deck gun, which had been blown off when the bomb exploded.
“We were elated,” Mr. Taylor said. “But it’s also sobering, because we just found 80 men.” The next day, Mr. Taylor and his crew held a ceremony to remember the sailors lost aboard the ship and called out their names one by one.
One of those names was John Patrick King.
His nephew John Bihn, of Wantagh, N.Y., is named after him. Mr. Bihn, who was born three years after the Grayback went down, remembers him as a constant presence in his maternal grandparents’ home, where a black-and-white photo of the submarine hung in the living room near a black frame holding Mr. King’s Purple Heart medal and citation. But in his family, the subject of his uncle’s death was “too sad to ask about,” Mr. Bihn said. “My mother would cry very often if you spoke to her about it.”
With no body to bury, Mr. Bihn’s grandparents, Patrick and Catherine King, memorialized their son on their own headstone. Under their names, Mr. Binh said, they had engraved, “John Patrick King ‘Lost in Action.’”
Mr. Bihn got a text message from his sister Katherine Taylor (no relation to Tim Taylor) two weeks ago, saying the Grayback had been found. She had gotten the news from Christine Dennison. “I was dumbfounded,” he said. “I just could not believe it.”
“I wish my parents were alive to see this, because it would certainly make them very happy,” he added.
In a video taken by the vehicle that surveyed the wreck, Mr. Binh said, the camera tilted upward at one point to show the conning tower, and a plaque reading “U.S.S. Grayback” was plain to see.
“It’s like someone wiped it clean,” Mr. Bihn said. “It’s like it wanted to be found.”