David,

Lucky for you, the U-505 is probbaly one of the most researched U-boats out there. Hopefully you are are aware of the display that will open this summer in Chicago. The curator of that display, Keith Gill is a pretty regular visitor to this forum has has been very generous in the past with information, especially for family members of it's victims.

If he doesn't reply to your posting in a day or two, try contacting him through the museum site.

I too had a report describing strange lights for the ships I have been researching (Arkansan & U-126 - another type IXC), suggesting communication between U-boats. After looking into the daily positions of all other U-boats on patrol at that time my attack occurred, plus the KTB, I ruled that out as a possibility in my case. The two best explanations provided to me were either life jacket beacons (which you've eliminated) and the glow of the red action lights inside the boat shinning up through one or more open hatches.

As you may or may not know, red lights were used on board to help the crew to retain thier night vision better when they went on watch (such as during a night surface attack that was common during the first half of the war).

Hope this helps,

Eric