"As dawn broke on June 6, 1944, in northern France, the Allies began an invasion in the works for years: D-Day, the start of Operation Overlord that turned the tide against Nazi Germany."
Foul weather forced Eisenhower to postpone Overlord until June 6. Two more weeks would pass before the moon and tides were again favorable for paratroopers landing inland before dawn and soldiers landing on the beaches at daybreak.
The decision to proceed on the sixth, during a predicted lull in the storm, caught German commanders by surprise. But some Allied landing craft and amphibious tanks sank in swells, and men who stayed afloat were seasick. Nausea mingled with dread as they disembarked under fire. “Many were hit in the water and drowned,” recalled Sgt. Bob Slaughter of the U.S. 29th Infantry Regiment. “There were dead men in the water and live men acting dead, letting the tide take them in.”
https://www.nationalgeographic.com/archaeology-and-history/magazine/2019/05-06/invasion-of-normandy-d-day/