Other mistake: During the credits, in the shot of the diner, the asian man sitting to the right glances right at the camera. (00:02:00)
Factual error: In relation to the position of the sewage workers shadow, and the way Jason kills him, there is no way that the splatter of blood would have hit the wall the way it does. In addition the blood looks like paint. (01:27:20)
Revealing mistake: Throughout the movie, the black cloth covering Jason's eyes under the hockey mask is really noticeable, especially when he grabs onto the rope to climb aboard the Lazarus. (00:15:25)
Other mistake: At the beginning when you see outside the museum, there's a man in a red T-shirt looking at the camera. (00:28:45)
Visible crew/equipment: Rennie and Sean get onto a train, Rennie spots Jason standing behind a door. When it does a closeup of Jason, reflected in the bottom left hand corner of the glass is a crewman with headphones on. (01:20:00)
Continuity mistake: When Sean is given the present by his father, there is a polystyrene pad next to the computer navigator, which is sticking out. In the next shot it's pushed in neatly. (00:14:25)
Continuity mistake: After Wayne shoots his friend, he looks through his camera. The timer on the camera reads "20:19." It cuts to another angle of Wayne, then back. The camera still reads "20:19" even though a few seconds passed in the other shot. (00:48:30)
Revealing mistake: You can see a faint red line on the Captain's neck, before it is cut. (00:39:10)
Continuity mistake: The towel on the guy's head in the sauna changes position between the shots. (00:28:15)
Revealing mistake: When Tamara pushes Rennie overboard, the ship stays in the exact same place, as if it was docked. In reality, the boat would have sailed on, leaving Rennie behind. (00:29:25)
Continuity mistake: When Jason grabs the policeman, the policeman's hat falls to the floor. In the next shot it's back on his head. (01:11:50)
Visible crew/equipment: When everyone is getting off the ship and into the small boat, it's raining. Jason is looking down at them - right when he is looking down you can see above him the sprinkler making the rain. (00:57:40)
Revealing mistake: When Tamara pushes Rennie overboard, the water is calm and there are no waves. (00:29:25)
Continuity mistake: When Rennie gets up and walks over to the closet, you can see some items on the side, such as a decorated silk cloth, a bag etc. When Jason then looks through the porthole into Rennie's room, the position of all the items are different. (00:21:35)
Visible crew/equipment: When Julius' head falls into the dumpster, a black cord can be seen pulling the lid down. (01:09:45)
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. (00:29:20)
Visible crew/equipment: When Sean finds Rennie in the alley recliner and kneels down to comfort her, there is a clear shadow of equipment on his jacket sleeve. (01:18:15)
Continuity mistake: When Toby turns up at the end, in the street, in the first shot of him his shadow is short. In the next shot it's very long. (01:32:15)
Continuity mistake: As Julius punches Jason on the roof, they pass the same skylight twice. (01:08:25)
Continuity mistake: When Julius is boxing with Jason, you see that his hands get cut up and are bleeding heavily during the fight. He continues punching Jason in the mask but never leaves a drop of blood on it. (01:09:20)
Chosen answer: To the best of my knowledge, this is just a bit of a continuity mistake. While previous films have not indicated Crystal Lake is connected to the ocean, this film portrays it as being connected. You just kinda gotta go with it for the movie to work.
TedStixon