Continuity mistake: In the beginning while Marlow struggles with the Japanese guy he's face down but in the next second is suddenly face up.
Continuity mistake: While Randa and Brooks are following Willis at the hall, there is a woman in red that passes by but in the next shot disappears.
Continuity mistake: At Packard's office, there is a brown cylinder piece that changes place between shots.
Continuity mistake: Before Mason gets in the plane she has her hair behind her neck, but when she talks with Packard she has it on the side and then back behind her neck again.
Continuity mistake: At the beginning before Marlow gets into the jungle he's wearing a yellow jacket that disappears.
Continuity mistake: At the time Marlow lands on the island the sun shines like it's noon but after he gets into the jungle the sun is lower, like it's dawn.
Continuity mistake: After Kong has destroyed all of the helicopters, Cole opens a tin of meat that is full to the top when it is first opened. But in the next shot, he takes one spoon full, and the tin has much less meat in than before.
Continuity mistake: When Col Packard shoots the "ugly bird" he is aiming left handed but after he shoots he is holding the weapon right handed.
Continuity mistake: When Weaver is on the top of the rocks to fire the flare gun to signal the boat, she is wearing her camera/tote bag around her and you can see it on her when she fires the flare at the skull crawler but when she is knocked off the rocks and falls backwards into the water, she isn't wearing the bag.
Factual error: All the helicopters shown have wire strike protection systems fitted. They weren't produced until 1979.
Answer: The chains are anchor chains from the ship wrecks that were there.