Shadow Divers

Chatterton wrote a letter and sent a copy to four experts, including U-boat sailor Merten. He received roughly the same information from them all: Only one Horenburg was recorded as having served on a U-boat, and he had been nowhere near the mid-Atlantic: Martin Horenburg, a senior radioman, had last been recorded onboard U-869, which Allied forces had reportedly sunk off the coast of Morocco in 1945. The entire crew was killed in the attack, and it was the only patrol U-869 had ever performed. It had sunk more than 3,000 miles away from Chatterton’s wreck.

Chatterton next met personally with the heads of the Naval Historical Center. Bernard Cavalcante, a US Navy archivist, was fascinated when Chatterton showed him the videotapes and revealed the wreck’s coordinates. Cavalcante reported that the US Navy had no reports that a U-boat had sunk near that location. He gave Chatterton access to the US Navy archives, as well as German information seized after the war. Still unsatisfied, Chatterton traveled with another diver, John Yurga, to Germany to inspect a war memorial inscribed with the names of all U-boat crew members who served in World War II and to visit the archive of Horst Bredow, the world’s leading German U-boat archivist.

Although Chatterton and Yurga inspected the memorial, they too found only one Horenburg. Bredow’s archives likewise turned up little except to confirm that Horenburg was last seen aboard U-869. Chatterton, Kohler, and Yurga scoured thousands of reports and narrowed down the possibilities to two boats, U-158 and U-851. Both of them were Type IX subs, like the wreck. U-158 had sunk near Bermuda, and Kohler argued that it could have traveled slowly up to the East Coast of the US before failing completely. U-851 was the boat that Merten mentioned, taken out against orders by Merten’s colleague and never seen again. Over dinner, Chatterton, Kohler, and Yurga discussed how to prove the sub’s identity. They realized that U-158 had a deck gun, an identifiable feature, while U-851 was a special class of submarine about 30 feet longer than a normal U-boat. If they could measure the boat and inspect it for a deck gun, they could conclusively determine the boat’s identity. In addition, they reflected on the horrifying experience of the sailors trapped in the sinking submarine, a fate detailed in many reports of wrecks during the war. British soldiers reported finding dismembered body parts and intestines among the wreckage of submarines, attesting to the violence of submarine explosions.

Feeling more confident, Chatterton, Yurga, and Kohler prepared for the next diving season. The location was safe to dive only in the spring and summer, so the next dive was scheduled for May 1992. Chatterton and Yurga experimented with a new diving tank technology called “trimix,” a mixture of helium with oxygen and nitrogen that could limit nitrogen narcosis, decreasing the danger of the bends and allowing for better peripheral vision, motor skills, and coordination. However, trimix was new, and no one could tell them whether it was conclusively safe, especially at such depths. Yurga and Chatterton made their own trimix in Chatterton’s garage and successfully used it to dive in shallower waters. They planned to use it when diving to the wreck in May. Kohler, uncharacteristically, was more cautious about using it, arguing that the risk of testing a new gas mixture during such a dangerous dive was too great. He pointed out that trimix had never been used in such cold water and required extra gear. He continued to use trusted traditional gear.

Meanwhile, alcoholism took a toll on Nagle, causing him to visibly deteriorate. Skinny and jaundiced, he seemed totally unprepared for the voyage. Chatterton assisted with navigation, and when they arrived at the site, the conditions were perfect. The sun was shining, and the sea was still and calm, and these factors created great visibility. Chatterton and Kohler descended together. The trimix seemed to be a success: Chatterton was more clearheaded than usual. Yurga descended with another diver named Lew Kohl, and both used trimix. However, Kohl, a less experienced diver, did not adjust his buoyancy to accommodate for the weight of the extra gear, flopping into the water and sinking rapidly. He managed to drop his weight belt and resurface, but he ascended too quickly and had the bends. It was a mild case but derailed the expedition. They rescheduled it for June 1992. On this trip, Kohl bowed out and was replaced by Chris and Chrissy Rouse, a father-son diving team. The two men were “excellent divers” who specialized in cave diving.

The divers returned to the wreck. Yurga explored the U-boat’s deck and determined that it had no deck-gun mount, so it could not be U-158. Chatterton measured the length of the sub as 250 feet. U-851 would have been 287 feet, so the mystery sub could not be U-851 either. Discouraged, the divers continued their research throughout the summer. Lacking other sources of information, Kohler, Yurga, and Chatterton discussed the issue of disturbing human remains. They decided that they would not rummage through the pockets of the dead, even if that meant never solving the mystery. Additionally, they would coerce other divers to follow the same rule: No one would disrespect the dead.

In October 1992, the Seeker returned to the wreck for the last dive of the season. Nagle, too sick to captain the boat, allowed Chatterton to pilot it instead. The Rouse divers could not afford trimix and planned to rely on air. This time, Chatterton found a small metal plate on which schematics were printed. Yurga identified the name of a German U-boat construction yard, meaning that they could significantly narrow down the identity of the ship by tracking the U-boats made by that yard. Meanwhile, Chris and Chrissy Rouse tried to extract a piece of canvas with German writing printed on it. Chris waited outside the wreck while Chrissy navigated inside. However, while trying to work the canvas free, Chrissy knocked a heavy metal cabinet loose, which fell over and pinned him. Chris freed him, but both had nitrogen narcosis and became confused, losing their way as they searched for the line to the dive boat. Chrissy, despite his experience and skill, panicked and made a break for the surface. His father followed, neither of them decompressing. Realizing the gravity of the situation, Chatterton called the Coast Guard to summon emergency helicopters. When rescuers pulled the father and son from the water, they had symptoms of severe decompression sickness, and despite the Coast Guard’s intervention, both died. Chatterton reflected that in 36 years of diving the Andrea Doria, only six people out of thousands of divers had died, whereas in one year of diving into the submarine wreck, three people out of only a handful of divers had died.