When Julius jumps out of the ocean into the boat, they lay him down, then turn him over and move him to the bench. In the closeup shot, McCulloch's hand is on Julius, but in the next shot, both hands are on the oars.
When Jason grabs the New York cook he is several paces to the right of the mirror, but when he throws the cook into the mirror Jason can clearly be seen in the reflection standing right across from it.
We are shown Jason's perspective as he is walking down a hallway towards the sauna. When Jason enters the sauna, we can clearly see there is no hallway across from the door which makes the previous scenes impossible.
After Rennie sees Jason's child ghost the first time, she leaves her room and the camera pans down the hall to reveal Jason emerging from behind a door with a dartboard on it. Before Jason is shown, look into the pictures beyond the door and you'll see a crew member signaling for Jason to make his appearance. After Jason leaves the room you will see the crew members arm closing the door in the same pictures glass.
In Part VII, Jason's suit was shredded so that you could see
his spine and kneecaps. Yet in Part VIII, he has gained a new suit even though he was beneath the water for quite some time. He is also now wearing black gloves although he did not have them previously.
When the ship takes off we see some scenes with lots of people on board having fun playing, dancing, etc. But as soon as the killing starts the extras magically disappear and we are left with the main characters. At least after the fire alert starts the other passengers should be alarmed and rushing for the lifeboats. Surely Jason didn't just kill everybody off.
Rennie's flashbacks suggest she was attacked by a young Jason under the lake. Jason drowned in 1957, and was a grown man by the time he began killing in the events of Part 2, set in the early 1980s. Several of the films take place years apart, so this film may possibly be set in the 1990s or even later (although the music and fashions suggest 1989). So Rennie could either not have seen a young Jason, or she would be much older than a high school student now.
Throughout the film, Jason's skin is grey, slimy and decayed, except for the pinky finger on his left hand, which is completely normal, protruding through his torn glove. This is especially noticeable in the extreme close up of Jason grabbing the railing of Jim's boat near the beginning.
When Jason throws Wayne into the electrical switcboard, Wayne's jeans light on fire before he hits the board. Also, as the spark causes the combustion, you can clearly see flammable liquid on his jeans.
When Shaun and Rennie run through the two glass doors leading down into the New York subway system, you can see Jason's shadow on the wall as he stands off camera and waits for his cue to walk on screen and kick his way through the glass doors
When J.J. is killed, she drops the guitar, and the boombox suddenly stops playing too. Additionally, blood flies at a piece of glass in front of the camera before Jason actually makes contact with her.
Rennie and Sean sit on the subway to get away from Jason. When Rennie sees Jason in the car ahead of them, they run toward the back. Several shots show the tunnel lights moving in the wrong direction (towards the back, which would indicate that they are running to the FRONT of the train).