Air Bombing and Frogmen aren't the right answers, soldier!

Because the steel obstacles and minefields are buried in sand aerial bombing would have had little or no effect. Frogmen were sent at night to destroy some obstacles, but there were far too many barriers for them to deal with. The extremely low tides on June 6th meant that the landing craft could avoid the obstacles sticking out of the water. The bad news was that this meant the soldiers had a very long distance to advance across a wide open beach to get to the German defences - and they were under fire the entire time!