Forgot to mention, I've never found a single site on the Nereus and Proteus. I have a picture of each (a stern shot and a bow shot) in an old and out of print book called the Devil's Triangle (try to guess what it's about
). The pictures are captionned as belonging to the US Navy.
No I don't think they were sunk by U boats (if they were, imagine the tonnage though
) - if they had been, there would probably have been some record and no U boats were in the area anyway. I guess it's possible though.
As for sinking bulk carriers in modern times, one actually broke in two and sank (the MV Flare) near St. John's Newfoundland, the province where I live, several years ago. The footage was used in the movie Godzilla, in the scene where the French "insurance agents" (French Foreign Legion) are interviewing the sole survivor, I think (on the TV in the room).