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.
Revealing mistake: When the Minotaur is born, he doesn't cast a reflection on the building right next to him.
Revealing mistake: When the Barrys cross through the glass door, for a couple of shots, Young Barry's face is replaced with a non-realistic CGI face with features that don't match the face contour at all.
Revealing mistake: Ariel swims underwater and opens a book with stiff and easy-to-flip pages that produce a flutter sound when turned. The paper should be either soggy, or with its pages stuck together or even dissolved, and in no case sound and look as if it were dry.
Revealing mistake: Just after Dante says, "There he is, the man of the hour. Roman," we see the bomb crash into 3 vehicles, with the middle one being a blue car. In the first shot, we see the blue car get damaged. In the second shot, we see the blue car is undamaged before it gets damaged again. (00:32:20)
Revealing mistake: While inside the tunnel in Rome, before the yellow Fiat makes a U-turn multiple skid marks from previous takes are visible. Though one might pressume that the marks were already there, they are at the same spot and have the same pattern as the skid marks that the cars make seconds later.
Revealing mistake: The ship is being attacked by a megalodon. The USS King is supposed to be in open ocean. When three sailors run to the left, we can see the ship is next to a dock. (01:01:35)