Visible crew/equipment: When Tamara pushes Rennie, as Rennie starts to fall you can see a crewmembers hands reach out to catch her. Look close and you can even see the red tee-shirt sleeve of the person. (00:29:20)
Visible crew/equipment: As Jason is walking down some steps, a little after he kills J.J., you can see the shadow of a crewmember pushing equipment, cast on the wall. (00:21:55)
Visible crew/equipment: When the boxing scene starts, as the camera pans past the punchbag, the shadow of the camera is clearly cast on it. Then as the camera continues to pan past the punchbag, you can see the sides of two crewmembers come into view (who are following the path of the camera.) They are both wearing a jumper and jeans. (00:23:05)
Visible crew/equipment: When Eva is in the disco, after Jason bursts in, as she pulls at the second locked door, you can see the reflection of two crewmember's faces in the silver disco pole. (00:45:30)
Visible crew/equipment: When Rennie is searching for Toby, the camera then pans to the games room, and reflected in the four pictures hanging up on the wall is a crewmember giving Jason a signal to come on cue. (00:26:00)
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)
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)
Visible crew/equipment: When Julius' head falls into the dumpster, a black cord can be seen pulling the lid down. (01:09:45)
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)
Visible crew/equipment: After Rennie and Sean pull the emergency break on the train, and get off, Jason follows. As he exits through the door, in the window to the viewers left is a reflector screen clearly reflected. (01:20:55)
Visible crew/equipment: After the police car is crashed, as it goes up in flames you can see a thick black wire trailing up into the police car's boot, which wasn't there before. (01:13:00)
Visible crew/equipment: When Sean and Rennie come up the stairs just before finding Sean's dead father, as the camera moves backwards, you can see the camera's shadow on the wall to the right. (00:39:40)
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