Izac later recalled that he was treated well while a prisoner, dining with the ship's officers and playing bridge and other card games with the crew. During political discussions on the boat, he also learned about the German mindset and conditions for German U-Boat crews, which were generally superior to conditions in other ships at the time. During this time, he began to take mental notes of the submarine and the routines and operations of her crew, hoping to gather intelligence that could be useful against German submarine efforts. He concealed his knowledge of German language which he used to listen in on the crew. Using maps and binoculars borrowed from the crew, Izac was able to ascertain the ship's return route to Kiel, which took it north of the Shetland Islands, into the North Sea and past Skagerrack and Kattegat in a bid to avoid minefields and patrols. He also learned of a rendezvous point used by U-boats near Denmark to avoid patrols, though was thwarted in his first escape attempt there. He also learned of at least one island where sub crews were commonly landing to poach mutton, which he considered ideal for a trap. Arriving in Kiel on June 10, he was transferred to , on which he was ferried to a prison camp in Karlsruhe. Conditions there were more difficult and the prisoners were fed less, so and he tried unsuccessfully to escape again.