These XB boats, designed in 1938, were laid down as ocean-going submersibles. They could carry up to 66 SMA mines in 30 vertical mine shafts, and up to 15 torpedoes. The XB class boats were special in that they had only two torpedo tubes, at the stern. As transport boats they carried freight containers in the mine shafts (or had the freight containers welded on top of the lateral shafts, preventing their use for mines). At 2,710 tons submerged and fully loaded, they were the largest German U-boats ever built, and they had to sacrifice diving speed and agility.

Six of the 8 boats built were sunk during the war (5 with all hands) but two survived the war. One survivor was U-234, which was infamous for its 560 kg cargo of uranium oxide en-route to Japan. Other cargo included two Me 262 jet fighters and 10 jet engines. The other type XB to survive was U-219 which reached Djakarta in December 1944 with a cargo including dismantled V-2 rockets for Japan.

These XB boats, designed in 1938, were laid down as ocean-going submersibles. They could carry up to 66 SMA mines in 30 vertical mine shafts, and up to 15 torpedoes. The XB class boats were special in that they had only two torpedo tubes, at the stern. As transport boats they carried freight containers in the mine shafts (or had the freight containers welded on top of the lateral shafts, preventing their use for mines). At 2,710 tons submerged and fully loaded, they were the largest German U-boats ever built, and they had to sacrifice diving speed and agility.

Six of the 8 boats built were sunk during the war (5 with all hands) but two survived the war. One survivor was U-234, which was infamous for its 560 kg cargo of uranium oxide en-route to Japan. Other cargo included two Me 262 jet fighters and 10 jet engines. The other type XB to survive was U-219 which reached Djakarta in December 1944 with a cargo including dismantled V-2 rockets for Japan.