U-550 Found...

The U-550 was a type IXC/40 German U-boat, commissioned on July 28, 1943 and sunk about 70 miles off the coast of Nantucket, Massachusetts on April 16, 1944 – less than 9 months later.  A dozen of the U-550's crew were rescued by the USS Joyce, one of the three ships that sank the U-boat.  The photo at right was taken during the fight that led to the U-550's sinking. 

Evidence suggests that several crewman (number unknown) survived after the U-boat sank and hit the ocean bottom, and then were able to escape using the standard breathing apparatus designed for that purpose.  These crewman appear to have survived for some time at sea, but then died – most likely from some combination of exposure, thirst, and hunger.

The wreck of the U-550 has now been found.  It's exact location has not yet been divulged, but it's within reach of expert divers.  Modern diving technology has made it much easier to reach deep wrecks, though it's still a very dangerous thing to do.  I suspect there will be some salvage efforts, though probably amateur, since (so far as I'm aware) there is nothing aboard the U-550 with the monetary or historical value that would justify professional salvage.