Plot hole: At the start of the film, a young Jürgen Voller gets hit square in the face, at high speed, by trackside equipment and gets knocked off the train. But somehow, he isn't killed and survives without so much as a scar on his face.
Continuity mistake: When the villains are following Indy through the caves, the old wooden bridge completely breaks and falls apart. However, when they make their escape across the same bridge, it's intact with only a couple of wooden slats broken.
Factual error: The four-barrelled Flak gun is shown running out of ammunition, namely a belt of rounds. This is most likely intended to be a Flak 38, which used twenty-round magazines, not belts. It had a relatively low rate of fire as the magazines had to be constantly swapped out, and two barrels were usually fired at a time. (00:16:58)
Factual error: When flying towards the time fissure, the German commander says that Hitler is awaiting info on the V-1 project. They're supposed to be heading for a date shortly before Germany invaded Poland. The V-1 project started in early 1942, and it wasn't named the "V-1" until June 1944.
Factual error: Basil Shaw is British, but the dates in his notes about the Antikythera are all written in American format (MM-DD-YY), as opposed to DD-MM-YY.
Other mistake: As the divers prepare to descend to the Roman shipwreck, none of their buoyancy aid inflation valves are connected to an air intake. This makes the rapid inflation, which happens on their ascent back to the surface, impossible. (01:15:15 - 01:15:50)
Factual error: The night before Indy dives on the Roman wreck, his co-star describes the plan. An initial 70ft drop, followed by a further 300ft descent to the sea floor. Essentially, if you breathe compressed air to equalise your lungs to the surrounding pressure, then you cannot ascend to the surface rapidly from that depth. Breathing normal air, you can suffer from oxygen toxicity at around 56m. Due to the partial pressure law, at 370ft/112m, you would need a heliox mix (10% oxygen) from a second tank to survive. (01:21:00 - 01:22:08)
Continuity mistake: After the Roman shipwreck, the Spanish flag on the dive boat goes from flapping vividly in the wind in one shot to then hanging limp in the next. This discrepancy is throughout all of the exterior dive boat scenes. This likely shows which clips were filmed on location and which were filmed in a studio. (01:09:40)
Factual error: The Siege of Syracuse occurred in 212 BC, during the Second Punic War, when Rome was still a republic. Some of the equipment the Romans are using in the movie, however, particularly their swords and helmets, are replicas of weapons dating to the later Imperial era.
Other mistake: In flashbacks, younger Indiana Jones has exactly the same voice as the older one.
Suggested correction: Harrison Ford's voice has always sounded the same. Watch any film he's done.
It's a noticeably "older" voice than in previous films when he was about the age his de-aged self is meant to be. I mean he's now in his 80s not 40s, of course his voice is different! An unavoidable mistake but still clearly different.
Harrison Ford's voice has definitely become pretty gravelly.
Factual error: Shaunette Renée Wilson's (Agent Mason's) costume isn't right for 1969. That specific type of colored leather jacket, eyeglass shape, and long collared blouse in that style of geometric print didn't start being worn that way until the early 1970s.
Other mistake: Towards the start of the film, at the end of the train crash on the viaduct, time seems distorted. By the time it's taken Indy to wade out of the river and walk up its bank, magically a troop of British soldiers appear from nowhere, having entirely and instantly overrun a train full of Nazis? (02:16:01 - 02:16:35)
Revealing mistake: Throughout the dive boat interior scene - after they dive on the wreck - various hanging items are swinging around randomly to give the impression the boat is rocking on the water. However, none of the key light shadows - from the exterior sunlight - move at all, indicating the boat is entirely static in a studio.
Continuity mistake: At the start of the film, towards the end of the steam train roof battle, as Indy jumps from the train (200+ feet into the rocky shallow looking part of a river), it's still fairly dark in the early hours of the morning. As he surfaces seconds later, it's considerably brighter. Then, as he walks up the river bank, morning is well broken into much brighter light. Assuming the scene is set around March/April 1945, sunrise in the Alps is unlikely to occur so rapidly. (02:16:01 - 02:16:35)
Other mistake: When the divers ascend from the Roman shipwreck, an odd sort of heat-seeking mini-torpedo or poison homing dart projectile is fired down from the surface. Any idea what this is supposed to be? The henchmen on the boat appear to be wielding a knife, a Luger, and a (wrong for the period) 1986 micro Uzi. (01:10:20)
Continuity mistake: Within the Roman shipwreck, Indy is grappling with his fear of snakes (eels) with his red flare; a torch light is briefly shone on his head from above. When the shot reverses to the diver at his rescue, she has no torch at all in sight. (01:11:12)
Other mistake: Whilst swimming towards the Roman shipwreck, the divers appear to be moving at a speed similar to an unrestricted diver wearing flippers. The drag resistance from the air pipe umbilical, together with the divers' lead boots, would make this an unfeasible maneuver in real life. Equally, the divers have no BCD or method of maintaining equal buoyancy and would sink to the seafloor - not swim like a fish. (01:13:14)
Factual error: Whilst Indy and friends dive the Roman shipwreck, they descend and ascend rapidly to and from the sea floor. The conventional method to dive at depth is to descend slowly - to equalise your pressure, as well as to ascend slowly - once more to equalise for the pressure differences. The 3-minute dive duration, with rapid descents and ascent, simply is not possible without the effect of causing serious trauma to the body. (01:09:30 - 01:14:50)
Continuity mistake: When Indy arrives in Tangier at Hotel Le Atlantique, it is evening. A party is going on in the hotel while the auction is being held. A discussion starts, and a fight breaks out. They go outside, and all of a sudden, it is daytime.
Other mistake: Dive boat interior, as the tablet is unboxed, there is a clear lens distortion as Indi looks round to his diver friend and the focus follows - giving a disturbing jolt to the image. (01:08:27)
Suggested correction: It just appears to be the result of the movie doing a slightly unconventional rack focus. I don't think that really qualifies as a mistake. If it does count, it opens far too big a can of worms in terms of various camera techniques being considered "mistakes."
