Continuity mistake: In the water tank sequence Cranston dives to the bullet holes to get air. When he dives down there is a camera shot looking up at him from the bottom of the tank showing that there is plenty of air left at the top, no doubt left there so that the actor would not drown. And; for the sealed tank to fill completely there must have been a way for air to escape rapidly from the top. When the tank was full water kept pouring in and would have escaped the same way. When Margo arrives there is no water coming off the top of the tank.
Continuity mistake: When Claymore shoots the invisible Cranston (The Shadow) in the water tank, a small volume of blood immediately starts dripping into the water. When Cranston materializes seconds later there is no blood whatsoever on him and no blood comes off him or his clothing when he dives into the water.
Continuity mistake: In the scene on the bridge near the beginning, when we first see The Shadow, he's only wearing a coat, not his cape. The shot switches, and when we again see The Shadow, he now has a cape. The cape must have been a CGI effect, because trailers and commercials show the same shot WITH the cape.
Continuity mistake: In the scene where Reinhart Lane finally defuses the bomb, he clips the red wire and Margo yells out "Green." and his hand holding the clippers are just above the red wire. In the next shot, his hand is nowhere near the wire and it changes back and forth during the rest of the scene.
Continuity mistake: When Claymore is shooting at Cranston, he misses three times, creating three bullet holes in the tank on the side opposite the door. When the tank fills Cranston swims over to them to get air, then swims across the tank to the door. When Margo Lane arrives and walks up to the tank the bullet holes have moved across the tank and are now next to the door. When Margo opens the door and the water rushes out of the tank the bullet holes next to the door have disappeared.
Continuity mistake: Near the beginning of the film when the police are investigating Shiwan Kahn's now empty coffin watch the policeman that delivers the message to the vacuum tube system. His ring starts on his right hand then switches to his left and so on. It's really funny. (00:34:03)
Other mistake: When Lamont walks into the alley to avoid being followed by one of Khan's warriors, he makes himself invisible, and his shadow vanishes as well. It's well noted at the beginning of the film that his shadow is always visible even if he isn't. Therefore, his shadow should still be seen on the ground and give him away.