The article is very interesting, but in part it has something of a sailor's yarn, with facts that could be connected but were not, e.g. the sinking of the IMPERATRIZA MARIA and the loss of UB 7, when the commander, Oblt.z.S. Lütjohann, had set the sinking as his goal. The sailor Max Krems was indeed a crew member of UB 7, but he was transferred to the naval hospital in Varna on September 18, 1916, as the commander suspected that he had apparently fallen ill with jaundice. UB 7 sailed for its last mission, which was scheduled for 8 days, on 27 September 1916. The boat should therefore have been back 15 days before the sinking of the IMPERATRIZA MARIA, and UB I boats were not designed for a 23+x day mission. It must be doubted that Max Krems was on board on this last mission. His name would have appeared in the official list of losses, as it was assumed in Germany that the boat was a total loss. A video of the dive to the wreck of UB 7 can be seen on YouTube. However, it would still have to be clarified in which direction the bow is pointing and whether the two torpedoes are still in the torpedo tubes. You can clearly see that the conning tower hatch is closed, which speaks against Max Krems' depiction.
The alleged sinking of the Russian submarine MORSCH in May 1917 by UB 42 (U 42 did not exist in the Imperial Navy!) is also untrue, as the boat was not at sea at that time.

Simon S.