The Abyss (1989)

Factual error: [Special Edition] The Statue of Liberty is incorrectly shown to be facing the Narrows bridge.

Revealing mistake: When the crane falls down in front of the rig and then over the cliff into the abyss it's as if the rig was already just a few yards away from the abyss but when the umbilical pulls the rig again (after Bud says to grab onto something) suddenly there's enough space for the rig to be dragged at least a few hundred yards as if the rig never moved from its touchdown position earlier in the film.

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Revealing mistake: Every time the aliens appear anything electrical shuts down but somehow Lindsay's camera is able to take pictures of the small NTI before the electricity powers back on.

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Revealing mistake: When Bud is unscrewing the trigger from the nuke down at the bottom of the abyss, there are no threads on the mechanism to require unscrewing. The part of the device that would have the threads is plainly visible.

Factual error: When Bud is dropped onto the spacecraft floor by the alien who rescued him, air trapped in his suit comes off in large bubbles. At 18,000 feet bubbles would be compressed so far that they would be BB size. Also, with all the movement Bud experienced on the way down, no air could possibly have remained trapped in the folds of his suit.