The Kriegsmarine was largely a defeated and spent force by June 1944. Allied air superiority and ASW had forced a reorientation of German naval strategy towards the North Sea and U-boat bases in Norway, which was a tacit admission of their defeat. The Norwegian bases were not subjected to the same umbrella of Allied air interdiction to the scale of their French-based counterparts. There were some U-boats still in operation in France, but as this map shows, they were on the wrong side of France to patrol and intercept the invasion flotilla. The Kriegsmarine's defense of the Channel was focused primarily upon E-boats and specialized minisubmarines like the Marder and Neger that would attack after the invasion had begun. There were some U-boats that also attacked the invasion flotilla, but between June and August, the Kriegsmarine lost 15 U-boats in the Channel.

Source

Tarrant, V. E. The Last Year of the Kriegsmarine: May 1944 - May 1945. Annapolis, Md: Naval Institute Press, 1994.