I skimmed through the movie; there were definitely some liberties taken with the actual events but the overall outline was accurate. Tirpitz was the sister ship of the infamous Bismarck; the Germans stationed it and most of their other heavy warships in northern Norway to threaten Allied resupply convoys headed to the Soviet Union. This required the Royal Navy to keep carriers and battleships in the North Sea to cover the convoys (the US Navy also kept at least one battleship in the area), which were needed in other theaters. The first attempt in October 1942 to take out the Tirpitz with "chariots," Operation Title, failed due to both craft breaking their tows in bad weather.
Operation Source used six X-craft, which were assigned to attack three separate German warships. The battleships Tirpitz and Scharnhorst were holed up in Kafjord while the "pocket battleship" Lutzow was holed up in Langfjord. X5, X6, and X7 were assigned to Tirpitz, X9 and X10 were assigned to Scharnhorst, and X8 was assigned to Lutzow. All six X-craft were initially towed across the North Sea by full-size S- and T-class submarines to a release point near the target, where the three-man passage crew would be replaced by a four-man operations crew. X9 broke its tow in transit and sank with all three members of the passage crew; the two side-cargoes on X8 began leaking and detonated when jettisoned, forcing the crew to abandon ship and scuttle X8. The operational crews boarded the remaining four X-craft on September 20, 1943 and traveled for two days to reach their targets.
Of the four remaining subs, X10 had to abort its mission due to mechanical and navigational difficulties; in any case Scharnhorst was out on maneuvers at the time. X5 disappeared with all hands and its fate is unknown; X6 and X7 managed to drop their charges under the Tirpitz but were attacked during their escape and abandoned. Six of the eight crew survived to be taken prisoner. The Tirpitz took on over 1,400 tons of water, had almost all of its turbogenerators knocked out, and one of the 15-inch main battery turrets was thrown from its bearings. Repairs took six months; another X-craft raid was ruled out as the Germans had tightened their defenses. As Tirpitz was getting up steam for full-power trials on April 3, 1944 a British carrier strike hit the ship and put it out of action for another three months. The Royal Air Force eventually sank the Tirpitz near Tromso on November 12, 1944 with Lancaster bombers using 12,000-lb "Tallboy" bombs.