[Senter Cove Guy]

I read the book in Oct. 2004 and bought the DVD of the PBS show in 2005. Both are excellent. Three people lost their lives while diving the sub (U-869) and John Chatterton, who retrieved the evidence that ultimately identified the sub, almost lost his after executing a special maneuver to get himself deeper into the sub and getting temporarily pinned under some wreckage that fell on him.

I had a chance to talk with John Chatterton at the 2005 Boston Sea Rovers conference in March 2005. He, Richie Kohler (another U-869 diver) and Robert Kurson (the author of Shadow Divers), made a presentation at the conference.

The DVD has a lot of great underwater footage plus some graphical animations of the special maneuvers that Chatterton had to perform to get deep enough into the sub to get the evidence. It also contains a lot of WWII information about German submarine warfare planning and a visit by Richie and John to a former U-869 submariner still living in Germany and to a relative, living in the United States, of one of the submariner's who died when the sub went down.

Chatterton, Kohler and other U-869 divers used a trimix gas (oxygen, helium and nitrogen) when diving the sub. The helium took the place of some of the nitrogen that normally would have been in the mix which has the effect of reducing the absorption of Nitrogen into the blood thus reducing the chances of getting the bends. They might have breathed pure oxygen during their ascent from 235 feet while stopping at pre-determined decompression depth stops to allow Nitrogen to purge from their bloodstream. A 20-25 minute bottom time dive at 235 feet requires somewhere in the 1.5 - 2 hrs of decompression stops I believe.