If you haven’t read D-Day, by Stephen E Ambrose, I’d really recommend it if you’re interested. All quotations are from Chapter 14 of the book.
They bombarded the crap out of the beaches. Several veteran soldiers have said the opening naval barrage on D day was one of the loudest things they had ever heard.
One of the Allied airborne troopers tells it this way. “The Barrage coming in was quite terrific. You could feel the whole ground shaking toward the coast. Soon they lifted the barrage farther inland. They sounded so big, and being poor bloody infantry, we had never been under naval fire before and these damn great shells came sailing over, such a size that you automatically ducked, even in the pillbox, as one went over, and my radio operator was standing next to me, very perturbed about his, and finally he said, ‘blimey, sir, they’re firing jeeps'”
A total of 68 destroyers participated in the bombardment of the 5 beaches.
Ambrose summarizes the reason why the success didn’t work in the following way.
“In short, a tremendous tonnage of shells hit the beaches and batteries. The results, for the most part, were terribly disappointing. As anyone who has visited the normandy beaches will attest, this was not because of inaccurate fire, but rather the result of German skill in fortification building… They [the batteries] took many direct hits, dozens in some cases, but even the 14-inch shells failed to penetrate. The shells made pock marks, the knocked away some concrete, they exposed the steel reinforcing rods, but they did not penetrate.”
However “Many of the German gunners inside were rendered deaf or knocked out by concussion” from being inside a concrete bunker.