A cross-section of Omaha Beach on June 6, 1944. It's not to scale—there were hundreds of yards of sand to cross at low tide. Sketch is a part of the Distinguished Unit Citation earned by the 16th Infantry (Click here to read the citiation).
On the following pages is a wide-ranging intelligence report on what the soldiers landing on Omaha Beach ("Beach 46") were expected to face. For them, one of the most important items appears on page 8 of the document: "There is a strip of shingle [the "shale shelf" in the sketch above], about 15 yards wide, extending along the entire beach at the high-water mark."
That strip of gravel was the only thing that kept many of them alive that morning because if they laid behind it, German machine guns could not reach them.