Continuity mistake: After Tamara comes out of the the shower she is completely dry. (00:36:00)
Continuity mistake: There is a large blue cooler by the stairs in the boat, under two postcards. But in the shot where Jason clips the harpoon, before shooting it, we can see the cooler has vanished. (00:07:40 - 00:09:00)
Continuity mistake: By the radio on Jim's boat is a bottle with a boat in it and the cork in the bottle is pointing to the left side. When Suzi gets up to check on the noise, the bottle is visible and the cork is now pointing to the right side. (00:03:45 - 00:07:30)
Continuity mistake: When Wayne is taping J.J., between shots his left hand moves from down by his side, to on the focus of his camera. (00:18:20)
Continuity mistake: When Jason grabs the man in the diner he is several paces to the right of the mirror, but when he throws the man into the mirror Jason can clearly be seen in the reflection standing right across from it. (01:24:35)
Continuity mistake: In the scene where Tamara gets out of the shower, her silk gown which hangs on the handrail changes position between shots. (00:35:45)
Continuity mistake: The shards of glass around the porthole change between shots, as Jason attacks Rennie. (00:53:40)
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)
Continuity mistake: The towel on the guy's head in the sauna changes position between the shots. (00:28:15)
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)
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)
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)
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)
Continuity mistake: When Sean, Rennie and the sewage worker walk down the sewers, in frontal shots and reverse shots, the sewage worker repeatedly changes from holding his flashlight by his side / out in front. (01:26:55)
Continuity mistake: When Jason is walking down the stairs toward J.J. his left foot comes off the last step but in the next shot it's his right. (00:20:55)
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. (01:27:55)
Continuity mistake: Jason's shown as being a regular faced boy of 8 or 9 when he drowned. This is inaccurate as the original Friday the 13th showed he was deformed as a child.
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