Continuity mistake: After Chris wakes up in the boat, the front of the boat gets stuck in some logs. The logs change position around the front of the boat between shots. Also, hay appears on Chris's shirt after she wakes up. (01:24:50)
Continuity mistake: The magazine Debbie reads in the hammock changes - look at the back cover when she climbs into the hammock with it. When she turns a page, watch closely and look at the back cover. It has changed. (01:02:05)
Continuity mistake: When Nick walks into the room, after Chris discovers Shelley in the cupboard, he leaves the door wide open. When the others enter the door is half shut. (00:27:55)
Continuity mistake: At the start in the van, the girl you see smoking dope hands over her cigarette to the other kid. She uses her index finger and her thumb with the cigarette facing downwards, but in the next shot she has got it between her index finger and middle finger and it is facing upwards. (00:18:35)
Continuity mistake: During the one brief scene where we see Jason unmasked at the end of Part 2 when he crashes through the window and grabs Ginny, we see Jason has at least a partial head of hair. In this film, however, he's completely bald.
Continuity mistake: Part 3 picks up just minutes after Part 2. It shows Jason removing the machete from his shoulder. His flannel shirt sleeves are unbuttoned, whereas they were buttoned up in Part 2.
Continuity mistake: The last thing Andy sees is he walks down the hall on his hands is Jason slicing straight downwards at him with his machete. But this would have bisected him lengthwise, not at the waist. When we see his body up in the rafters, he's been sliced into a top half and a bottom half.
Continuity mistake: When Loco goes to the barn, he has a cigarette in his mouth. When he goes into the barn, it has gotten shorter although it's not lit.
Continuity mistake: Chris puts her lantern down on a table in the sitting room, before going upstairs and finding the flooded bathroom. Later when Rick's body is thrown through the window, the lantern has vanished. (01:08:30 - 01:12:25)
Continuity mistake: When Fox looks up the ladder, we see the edges around the ladder hole, and the floor is covered in hay. Moments later, when Loco looks for her, he climbs up the ladder, and there's no hay around the hole. (00:38:05)
Continuity mistake: When Shelly and Vera are walking out of the store, Vera stuffs Shelly's wallet into her beige pants. Later, while sitting on the dock, she pulls it out of her pink pants. She doesn't have a change of clothes with her. (00:31:05 - 00:56:40)
Continuity mistake: Jason has dark Khakis throughout the film, until the very end. When the cops are at the house, his body is in the barn wearing blue jeans. In part 4 he is still in blue jeans, but then changes into dark Khakis after leaving the hospital.
Continuity mistake: When Chris is in the sitting room, Rick's body is thrown through the window. When Rick lands on the floor a shard of glass slides down and lies on his cheek. In the next shot it's gone. (01:12:10)
Continuity mistake: When Vera says "I never said you were a nothing." to Shelley you can see Shelley holding the harpoon pointing up. When it cuts he has it lowered out of sight. (00:54:30)
Continuity mistake: When Fox closes the door at the barn we can see she is closing the right door. When it cuts from the inside we can see her closing the left door. (00:36:25)
Answer: Friday the 13th Part III in 3D is also available on Blu-ray as part of a set of all the films from 1980 to the reboot. I know because I own it. There are two pairs of 3D glasses included in the tin.
Alan Keddie