The ship used in the movie is a coal ship called "D/S Hestmanden", built in 1911 and restored to working condition after decades of deterioration. The ship was used both in WWI and WWII on convoys and is now a museum ship.
The movie takes place in the summer of 1942, during the convoy of PQ-17. Of the forty-one ships which left Iceland, three were forced to return, and twenty-four were sunk. Ten merchant ships (one British, six American, one Panamanian and two Russian) and four auxiliaries reached Archangel, and delivered 70,000 tons out of the 200,000 which had started from Iceland. Fourteen American ships in all were sunk.