Other mistake: When Chief Phillips tries to kill Captain Willard there's a shot of the captain's back in the bright sunlight. If you look closely at the center of his back below his right shoulder there's a pressure mark similar to what you see on a hot summer day after a person gets up from sitting in a beach chair for a while. On the PBR we see Martin Sheen's character standing for a long time throughout the entire scene, but he was definitely sitting for a while before this particular shot was filmed. The pressure mark is not in the previous shot. (02:23:20)????
Continuity mistake: When they first approach Dennis Hopper we see the water on the left side of the boat past where Lance is sitting and there are no flames on it. After Hopper jumps on the boat and goes to shake the captain's hand we see an oil slick burning in the middle of the water. (02:29:40)????
Continuity mistake: After Dennis Hopper walks around to the other side of the bamboo cage Captain Willard turns around to look at him. Now both his upper and lower lips are parched but when we saw him in a close-up before when Dennis Hopper said, "he likes you, he really likes you" only the captain's lower lip was parched. (02:43:50)????
Continuity mistake: As they pull up next to the Vietnamese sampan, Chief Phillips moves the spotlight on top of the PBR with his left hand so it's pointing at Chef as he takes the papers from the fishermen. Thirty seconds later there's a wide shot of both boats as Chef reads the papers and we see the spotlight back to where it was before facing away from Chef even though Chief Phillips doesn't touch it again. (01:35:05)????
Revealing mistake: As Captain Willard takes his second swing at Colonel Kurtz there is a "spark" superimposed against the wall behind his head, which is to depict the contact point of the blade to the wall. However, the blade is actually resting on the Colonel's back, nearly a foot away at that time. (03:07:45)????
Continuity mistake: In a close-up Chief Phillips he says, "sampan off the port bow" and we see a kaki green T-shirt hanging next to him at the right of the screen. A couple of shots later Captain Willard says, "what up chief" and Phillips takes the T-shirt down. In the next wide shot of the boat the T-shirt is back. (01:34:15)????