Happy to share that I finally got my hands on a copy of Shadow Diver. Boy, am I glad this thread directed me to it. It is a compelling read. I'm at the part where Chatterton, ascending on the anchor line with his goody bag of definitive china (with its eagle-and-swastika markings), caught up to Kohler. And they were either going to come to blows OR form a tentative bond. What a pleasure to read, thanks for the recommendation!

P.S. I was also fascinated by Drozd's story (how he died with a full air of tank on his back).

As well as with the contention that wreck divers plan their dives in their heads all the time even when, on the surface, they're paying their bills and other such "mundane" stuff.