The "real" story on that is amazing, the heavy water the Nazi's did manage to make (before the Norwegian resistance fighters were able to sabotage the facility) was put on a ferry and that cargo was supposed to be put on another ship to take it back to Germany. But there was a commando who managed to slip on board and place explosives in the keel hold which sank the ferry and it sank in one of the deepest parts of the lake on which it traveled.
In addition to that bomb, there was actually young Norwegian couple who had smuggled a second bomb on board, and they were prepared to plant it and set it off if the first bomb did not detonate. They took the job knowing full well that they would likely die if the bomb went off, or if they were caught even smuggling their bomb on board, much less caught trying to plant it.
I will definitely watch this one.