Divers Tell Tale Of Mystery Sub

U-Who? 6-Year Search Nets Answers

(CBS)  But on dive after dive, nothing they found had any kind of markings identifying the U-boat. The divers nicknamed the wreck the "U-Who."

German sailors called U-boats “iron coffins,” because three out of every four were lost at sea with all hands.

"When you go inside this U-boat, the viciousness of WWII is really right there, apparent," says Kohler. "It’s apparent the in the grotesque destruction inside the submarine. It’s apparent in the fact that there are these human remains and skulls, literally at times peeking right at you, peeking through you. And these people, at least to me, wanted me to find out who they were."

Finding out for Brzezinski and crew meant taking a small boat three hours — and 60 miles — out into the Atlantic, to where the wreck sat on the bottom.

Amateurs cannot dive 230 feet, so cameraman D.J. Roller, who specializes in deep-water photography, joined Chatterton and Kohler on the dive. Divers wear about 250 pounds of gear: fish out of water on the boat, but right at home in the sea.

It took the divers only about 5 minutes to follow the anchor line into the dark waters that hid the wreck. Down there, the pressure is nine times what it is at the surface.

The wreckage is strewn all over and the sub’s hull is torn — signs of the powerful explosion that sank the U-boat six decades ago.

That’s what leads Chatterton and Kohler to believe that the U-boat was sunk when one of its own torpedoes — packing 700 pounds of high-explosives — malfunctioned.

Things had changed since their first dives down there. The tides had ripped away parts of the sub's outer skin and pulled out objects like cooking pans, which Kohler found in the ship’s galley.

"There is no environment more intimidating than being inside a shipwreck in deep water by yourself," says Chatterton.

Steve Feldman was part of the team on the earliest dives. He apparently lost consciousness while exploring the "U-Who" and drowned.

"There is a significant amount of risk," says Chatterton. "And if you really want some kind of safe, wholesome family activity, this is definitely not it."

On their return to the wreck, Chatterton and Kohler could spend only about 25 minutes exploring on the bottom. It took more than twice as long to return to the surface, because they had to stop often to decompress.