The password that Hardt is to use for his contact is the opening line of Heine's poem Die Lorelei, in which a beautiful woman who lures sailors on the rocks is used as a symbol of homesickness. When his crew joke about him spouting love poetry to a woman in the dark, they miss half of the point.
Local information form Orkney reports that it may have been the St Ola 1 that appeared in this film apparently sunk by U29. In real life the St Ola 1 served the route Thurso to Stromness between 1892 and 1951 with few cancellations in rough weather for the safety and comfort of passengers.
St Magnus (the name of the steamer sailing from Longhope for St Romness and Thurso during the closing stages of the film) is the Patron Saint of Orkney. There have been several ships in that area with the name St Magnus.