New German submarines are causing major problems for the Allies. Type XXI boats include snorkel breathing systems to run diesel engines under water. Their periscope, snorkel, masts have a special coating to avoid radar detection. These boats are fast and very difficult to detect. Had these gone into widespread use the Allies would have had major problems!

German E-boats and small craft continue operating out of Holland against Allied shipping in the North Sea and English Channel, and are now joined by "Seehund" midget submarines. The new craft enjoy some success, but mines remain the biggest problem for the Allies at sea. Allied air and sea patrols and minesweeping keep all these dangers under control. U-Boats still take a steady toll of shipping in the inshore campaign and sink two corvettes, but at a cost of nine U-Boats sunk by escorts or Allied minefields.