Factual error: When Lieutenant Colonel Packard meets war correspondent Weaver, it is mentioned that she was embedded with MACV-SOG in Vietnam. MACV-SOG was a top secret group that wasn't officially acknowledged until the '80s. There is no way that they would have allowed a reporter to be connected with them.
Factual error: In the scene at the Bangkok docks, the ship has the name Athena but with the Greek letter Lambda instead of each capital letter A. This would make the name something like Lthenl, and is a nonsense mix of Greek and English (Roman) letters.
Factual error: In the beginning Packard is in his office and opens a brown cigar box. That is a Rocky Patel box that wasn't developed in the cigar industry until 1995.
Continuity mistake: When Packard is pointing a gun at Randa it changes design between shots.
Factual error: In the opening scene, Marlow's P-51 Mustang has D-Day invasion stripes. These were used in Europe, not in the Pacific where the movie takes place. Even if the plane were transferred, it would have been repainted.
Continuity mistake: When they kill the big spider, its guts spill over one of the soldiers, but in the next shot, his face is clean.
Continuity mistake: While Cole is eating his helmet moves between shots.
Continuity mistake: While Marlow is cutting off his beard Nieves is besides him but disappears in the next shot.
Continuity mistake: After Kong saves Mason her body changes position on his hand.
Continuity mistake: When the crew gets to the island, Mason is taking some pics with a soldier behind her that disappears between shots.
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: When Col Packard is introduced, one can see on the left side of the desk behind him a wooden object beside a picture. In the next shot that object moves to the right behind the radio, only to return to the picture in the following shot. And it moves after this shot again behind the radio, and then stays there. (00:10:00 - 00:11:00)
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: 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.
Answer: The chains are anchor chains from the ship wrecks that were there.