Aside from the ineffective air bombardment, the naval bombardment was not effective either:
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. Seaman Ian Michie, on HMS Orion, a cruiser, was right when he said, "Our shooting was very good and direct hits were soon being recorded. We scored thirteen direct hits on the battery before shifting target." But at Longues-sur-Mer, Pointe-du-Hoc, Port-en-Bessin, St.-Marcouf, Azeville, and the other batteries, the casemates stand today, battered but unbroken. They took many direct hits, dozens in some cases, but even the 14-inch shells failed to penetrate. The shells made pock marks, they knocked away some concrete, they exposed the steel reinforcing rods, but they did not penetrate.
Many of the German gunners inside were rendered deaf or knocked out by concussions. An official report from the Royal Navy admitted that "no serious damage either to the concrete structures or the guns in the strong points" was achieved, but pointed out that the shelling "effectively neutralized the positions by terrifying the enemy personnel in them and by preventing them from manning their weapons and firing on the troops during the landings."
That was wishful thinking. Between the lifting of the naval bombardment and the landing of the first waves, many Germans managed to man their guns and commence firing. Inaccurately, it should be added: they had no spotter planes, and the forward observation posts on the edge of the cliffs were blinded by the smoke, so although they dueled with the battleships and cruisers, sitting at anchor, they scored no hits.
The smaller batteries, pillboxes, and Tobruks, the ones right on the beach or in the bluff above Omaha, also took a pounding and survived. Those on the beach had embrasures opening to the sides, not out to sea, so as to deliver enfilading fire parallel to the shoreline while being fully protected from fire from the warships. As the first wave hit, they came to life, delivering a withering fire at the tanks and infantry.
From the point of view of the soldiers going ashore, the great naval bombardment was as ineffective as the great air bombardment. According to Admiral Morison, the reason was "not enough time was allowed," and the fault was the Army's, not the Navy's, because the Army did not wish the bombardment to start before daylight. In Morison's opinion, H-Hour should have been postponed to 0730 "to give naval gunfire more time to play on beach defenses."
Stephen E. Ambrose, author, "D-Day June 6 1944"