Revealing mistake: In a scene where the canoes are shooting the rapids through a sheer cliff you can clearly see a stuntman climbing out of the water onto the rock.
Revealing mistake: When the mountain man is grinning at Jon Voight tied to the tree, you can see that his "missing" front tooth is actually painted black.
Visible crew/equipment: When Voight is making his way down the cliff face, he is rappelling. You can see a crew member feeding him rope at the top behind the trees.
Revealing mistake: As Voight starts to climb down the cliff with the rope, a safety wire is visible to the right of him. (01:20:10)
Continuity mistake: Burt is lying at the bank with broken leg flesh dangling. Next shot different angle, not dangling, then dangling again.
Continuity mistake: In the scene where Lewis and Ed are in the canoe after setting up camp and Lewis is bowfishing while Ed is drinking beer, Lewis shoots a trout. You can clearly see the arrow hit the fish just behind its head in a close-up shot. When Lewis pulls the fish in, the arrow is through the middle of the fish's body.
Revealing mistake: After Jon Voight has killed the mountain man and has tied a rock to his body so he can dump him into the river, the "dead" man takes at least two deep breaths right before he is rolled off the rock and into the water. In that same shot where you see his chest heave and him noticeably breathing, he also flinches and moves the pinky finger of his left hand.
Continuity mistake: When Burt's canoe comes up between two rocks, as the wooden canoe breaks in two, he had just passed through the same two rocks seconds earlier. (01:02:05)
Revealing mistake: In the famous "dueling banjos" scene I noticed several errors revealing that the actors are not really playing their instruments. This happens throughout the whole scene. The banjo player is using a different picking technique than would be necessary to create the music heard. His finger patterns on the fretboard don't match the sounds heard. The guitar player strums when you hear individually picked strings and visa versa. Again, his fretboard fingering does not match the music heard.
Continuity mistake: Just before the end, when going through the rapids, Burt Reynolds' life jacket moves around between shots. It's higher and lower depending on the angle.
Continuity mistake: When Jon Voight clings to a rock in the river, the rocks on the bank are the same rocks his canoe passes later as they flee in the canoe. (01:02:30 - 01:27:30)
Continuity mistake: When Ed loses control of the canoe and is trapped between two rocks, the other canoe strikes his and breaks it in half sending him and all of the contents of the boat, including his hunting bow, over the falls. Ed tumbles down the falls with nothing in his hands. In fact at one point he tries to scramble out of the water using both hands in the attempt. Yet two shots later he suddenly has his hunting bow in his hands. (01:02:05 - 01:02:50)
Factual error: In the beginning of the film the setting is very late summer or early fall as evidenced by the reference to getting back home in time to watch the football game on Sunday. Yet the deer that Ed shoots at is in the early stages of antler growth that appears to be more typical of late spring or early summer. The deer also appears to be some exotic species, not one of the whitetails that are native to Georgia.
Revealing mistake: The entire sequence of Voight climbing the cliff face is shot day for night, meaning the scene is supposed to take place during the night but was shot during the day. This is painfully obvious by the amount of contrast in the scenes we see sky (and the colored shots when he is on top of the cliff). When the camera pans up, it is a blue sky day but the scene takes place at night.
Continuity mistake: In the scene after burying the mountain man when Drew is paddling through the rapids, he is not wearing a hat. In the next shot he is, then he isn't, then he is, then finally he isn't, right before he is killed.
Revealing mistake: When Voight goes over the waterfall just after his canoe breaks in two, it is a stuntman.
Answer: No wound. Shook his head and dove from the canoe. Refused his life jacket. Just ridden with guilt as he was dead set against burying the hillbilly.
It's ambiguous. In an unused shot from that scene, Drew does grab at his head before falling overboard. Still, I too think he simply passes out from the stress.