Continuity mistake: When Rennie is being pushed overboard, notice the guys sitting in the background wearing a blue shirt. When it cuts from below the ship, as we see Rennie falling, the guy is gone. Also when Miss Van Deusen goes for the life ring, we see from below the ship that the guy is gone. But when it cuts he is there again.
Continuity mistake: The black sludge on the girl's white pants when she's in the sewer at the end is constantly changing. It sometimes changes position or isn't there at all in later shots. The best example is when she lures Jason away from the guy that just got knocked out and runs into the dead end. She slides down the wall next to the toxic chemical container and the back and sides of her pants are completely covered in the black sludge, when she runs away, her pants are totally clean.
Continuity mistake: Jason's clothes change quite a bit from the previous film, in part 7 they were torn to shreds so much so you could see most of his rib cage and spine and he had tan work gloves on. Now the clothes are mostly in one piece and the gloves are black or dark blue.
Continuity mistake: Rennie's visions of Jason as a boy change their appearance constantly throughout the film. At some points he is bald and deformed, much like how he was in the original film. At other times he appears as a normal, non-deformed boy with a full head of brown hair. At some moments he even appears as a mix of both (with a deformed face, but a full head of hair). This inconsistency is never explained or even acknowledged.