SHADOW DIVERS: The True Adventure of Two Americans Who Risked Everything to Solve One of the Last Mysteries of World War II

By Robert Kurson. Random House. 375 pp. $26.95

Among scuba divers, those who explore deep-lying shipwrecks are a tiny elite, revered for risking their lives just to recover, say, a dinner plate from an ocean liner's dining room. Recently a group of such daredevils retrieved a more precious artifact. Acting against government objections, they salvaged a small but intriguing scrap of history: a relic from the critical World War II struggle for control of the North Atlantic. The divers' story, which stretches from the ocean floor off the New Jersey coast to the German shipyards of Bremen, supplies the remarkable narrative spine of Shadow Divers, a captivating first book by freelance journalist Robert Kurson.

In 1991, a group of deep-wreck divers was investigating a curious large sunken object, originally located by a fisherman's electronic bottom finder, 60 miles off New Jersey. They found the wreck of a submarine that nobody had known was there. The early recovery of two white china bowls engraved with black swastikas and the date 1942 showed that the sunken craft was a World War II German U-boat. But which one? As many as 65 U-boats disappeared without explanation. Neither the U.S. nor the German navy nor private military historians had a record of a sunken submarine within 150 miles of the site.

Two New Jersey divers -- John Chatterton, who was part of the group that discovered the U-boat, and Richie Kohler, who joined the project shortly afterward -- spent the next six years leading an effort to identify the ship soon dubbed the "U-Who." They and others made repeated dives to examine the wreck, swimming with utmost caution through the submarine's cramped, debris-strewn passageways to hunt for clues while trying to avoid disturbing the white bones of dead German sailors just inches away.

Their discoveries -- a knife with a seaman's name carved in the handle, a metal engineering diagram identifying the shipyard that built the vessel -- gradually helped them close in on the submarine's identity. Some clues suggested it was U-857, which torpedoed an American tanker off Cape Cod in April 1945 and was subsequently attacked by the destroyer U.S.S. Gustafson. That submarine could have limped southward toward New Jersey before its end. Other evidence pointed to U-869, but records said that vessel was sunk off Gibraltar. Maybe it was U-851, whose commander, Hannes Weingaertner, was so eager to hunt American merchant vessels in the New York shipping lanes that he might have ignored orders to head to the Indian Ocean.

Even though they lacked academic training, Chatterton and Kohler did extensive research in American, German and British archives. To their surprise, they discovered that numerous details from official war records and widely accepted histories were flat wrong. As Chatterton wrote to Kohler from Germany, after interviewing one of that nation's most esteemed submarine experts: "We know more than they do. We must go back to the wreck."

Robert Kurson relates the tale of Chatterton and Kohler's six-year quest with drama and authority, and in mostly elegant prose. His book will in all likelihood join the company of such compelling and successful narratives of men doing deadly battle with nature as Jon Krakauer's Into Thin Air and Sebastian Junger's The Perfect Storm. Yet Chatterton and Kohler were also doing battle with a historical riddle. Once Kurson provides an account of how they solved it, he reconstructs the lives of some of the submarine's lost officers and crew, and effectively chronicles their preparations for what turned out to be their final voyage. He quotes from the commander's last diary entry before departure, an emotional note addressed to his 3-year-old son: "A few days ago, mean 'Tommy' [the English] dropped a lot of bombs and it was very loud. You were very quiet and you hid your little head under Mommy's coat. . . . Soon, Daddy will have to go out to sea with his U-boat, and our most ardent hope is that we will all see each other again soon, in good health and in peaceful times."

Kurson bases these two historical chapters largely on interviews in Germany with relatives and acquaintances of the dead. One of the sources, Herbert Guschewski, was a radioman assigned to the ship who was left behind when he fell ill days before it sailed. "Thank you for caring," Guschewski told Kohler when the American visited his home in a small town near Munich. "Thank you for coming here." As Kurson writes, this response was especially gratifying to Chatterton and Kohler, since authorities had discouraged them from exploring the U-Who to avoid disturbing a sea tomb -- and by extension, upsetting the sensibilities of the then-unknown survivors. The German Embassy in Washington formally asked them to call off the search, and the U.S. Navy declined to assist the effort.

Shadow Divers draws most of its drama, however, from the high-risk world of deep-wreck diving, which numbers at most several hundred enthusiasts out of 10 million certified scuba divers in this country. Whereas recreational divers rarely venture below 130 feet, the maximum recommended by most scuba organizations, deep-wreck divers go to 200 feet or deeper to probe alluring vessels like the famed Italian liner Andrea Doria, which sank off Nantucket Island in 1956. (Chatterton and Kohler went 230 feet deep in their explorations of the U-Who.)

Deep-wreck divers first must be prepared to do battle with nitrogen gas. It is the largest component of air, and so usually harmless. But under the high water pressure that divers experience, nitrogen can turn lethal. The buildup of the gas in the brain causes nitrogen narcosis, a kind of drunken state that narrows one's field of vision and impairs manual dexterity. Hallucinations can occur; in one, a diver reported he believed a lobster was talking to him and providing bad advice about what to do in a dangerous situation.

The other, better-known risk is the bends. If a diver returns to the surface too quickly, the sudden expansion of tiny nitrogen bubbles attacks the joints, nervous system and lungs. The result is agonizing pain, which can be permanent. To avoid the bends, a diver must return to the surface gradually, to allow time for decompression.

Finally, wreck divers routinely swim and crawl through treacherously narrow corridors and rooms, where a single piece of jagged metal or a stray cable could tear their equipment or ensnare their breathing tubes. It's easy to stir up silt or oil that reduces visibility to zero. Deeply competitive divers place a premium on probing places where it's impossible to know the dangers in advance. "It is one thing, wreck divers will tell you," Kurson writes, "to slither in near-total darkness through a shipwreck's twisted, broken mazes, each room a potential trap of swirling silt and collapsing structure. It is another to do so without knowing that someone did it before you and lived."

If anything, the risks in exploring the U-Who proved to be greater than the norm. On one trip, a shark stalked one diver, and a Coast Guard helicopter evacuated another with a mild case of the bends -- and that was not even one of the worst days. Efforts to unlock the U-Who's secret killed more than one diver, and the descriptions of those trips are among the book's most gripping passages. Even the climactic dive, which yielded the decisive bit of evidence that finally identified the submarine, was steeped in life-threatening danger: Unexpected delays meant that the diver came down to the last breath in his tanks.

Shadow Divers also excels in its rich portrayal of the two protagonists' personal motivations and psychologies. Chatterton is an especially compelling figure. From his time as a fearless medic in Vietnam, he developed a strict code of personal conduct that led him to become one of the most successful deep-wreck divers of all time. In a single year, in between dives to the U-Who, he discovered and/or identified four other notable shipwrecks. Unlike most wreck divers, he prized patient, systematic planning and work aimed at adding to the historical record. While most wreck divers live for artifacts -- underwater fistfights have erupted over disputed finds -- Chatterton gave away valuable objects that he'd recovered from the Andrea Doria. "How many teacups does one guy need?" he asked.

Kohler, for his part, was driven by a desire to honor the 56 dead German sailors by discovering their identities and providing their descendants with an accurate account of their demise. While the U-boat crew died in service of a hateful cause, both divers -- as well as Kurson -- clearly respect the Germans' military professionalism and courage as the war turned against them. The U-boat service suffered a death rate of almost 55 percent, and the Germans talked of a "sour pickle time" when Allied technology and resources attained such superiority that U-boat crews were less likely to kill than be killed. "No branch of a modern nation's armed forces had ever sustained such casualties and kept fighting," Kurson writes. "The Allies had predicted mutinies aboard these doomed U-boats. That never happened. The Allies had expected surrender from these doomed U-boats. That never happened, either."

Occasionally Kurson's writing is excessively flowery, and his tone relentlessly earnest. He turns suddenly to descriptions without explaining how he got the information. These are minor criticisms, however, and a Note on Sources at the end provides a full account of how the research was conducted. His assertion in an Author's Note seems entirely credible: "All of it is true and accurate. Nothing is imagined or interpreted, and no literary liberties have been taken." Shadow Divers is a masterful work of reporting and writing, about an intriguing historical mystery solved by divers who go where only a select few would think to follow. Kurson notes that the highest compliment that circulates among deep-wreck crews is: "When you die no one will ever find your body." Yet Kurson's narrative leaves you convinced that no one dies out of range of these divers. *

Robert J. McCartney, a former Germany correspondent and foreign editor of The Post, is now its assistant managing editor for continuous news.