Why didn't Hitler destroy the Allies in Dunkirk Bay?

During these days' retreat, it was mostly rainy days in Dunkirk, filled with fog, light rain and smoke, which made the German Air Force only carry out large-scale bombing for two and a half days on the afternoon of May 27, May 29 and June 1 day, and the rest of the time was either a destructive air raid by a small formation of three or five planes, or it was simply not dispatched. At sea, the English Channel, which is famous for its strong winds and waves, has been surprisingly calm recently, which has made many inland river vessels in Britain join the retreat and played a significant role. In the soft beach of Dunkirk, bombs and shrapnel dropped by German planes are difficult to fly effectively, and their lethality is greatly reduced. The defenders bravely resisted the German attack and covered the main retreat. Especially the last defenders, the French 1 Army, held their positions to the death, knowing that it was difficult to get out. The pilots of the British Air Force tried their best to provide cover for the troops. Some pilots flew three or four times a day, so that there were British planes all over the Dunkirk beach, which dealt a heavy blow to the incoming German planes. The officers and men of the retreating troops kept strict organizational discipline and order while waiting to board the ship, which made the whole retreat process very smooth; The organizers of the Great Retreat, those naval officers, with their excellent organizational skills, coordinated hundreds of various ships and used all methods and equipment to repatriate 338,000 people safely to Britain. German command error. On May 24th, guderian assembled tanks to attack Dunkirk, asking Hitler to allow his troops to storm, break through the blockade of the allied forces, and rush into the port area of Dunkirk, giving the British and French allied forces a final blow. Hitler was afraid that the Dunkirk port area was low-lying and the canals were vertical and horizontal, which made it unsuitable for tank fighting. At this time, Marshal Goering, commander of the German Air Force (seemingly just bragging), volunteered to kill the remaining Anglo-French Coalition forces with air bombers and closed the English Channel, which was recognized by Hitler. The Germans missed the opportunity to defend the blockade of Dunkirk. Hitler found that Goering's cowhide had burst, and it was too late to send guderian to attack.