Continuity mistake: In the film Jason kills the guy in the sauna with a hot coal into his stomach, and there's no blood. When Jason leaves you can see the guys chest and now it's covered with blood. (00:28:45)
Continuity mistake: When Jason is holding Eva in the air, he lifts her up higher towards the ceiling, but in the shots of her feet, they stay in the same position.
Continuity mistake: Crystal Lake goes from a lake surrounded by land in previous installments to suddenly having the space for a small yacht and a channel that feeds right to the open ocean.
Continuity mistake: When Rennie and Sean are on the ladder in the sewer Rennie's position changes between shots. (01:29:50)
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.
Continuity mistake: In the film Sean and Rennie are on board the Lazarus. Sean puts both of his hands into his jacket pocket to get Rennie's gift. He never hands it to her, but In the next shot she has it in her hands. (00:16:55)