A late uncle of mine was a radio operator on a US merchant vessel that landed supplies at Omaha on D+1. He was able to go ashore for about an hour. A veteran of the perilous North Atlantic convoys run, he was pleased to see the devastation wrought on the German positions and an open wire cage holding a batch of miserable looking German prisoners under guard.
Imagine sleeping on a ship knowing that UBoats are sinking ships all around? Make for some insomnia?