Goofs

In the scene where a man's head is pulled off, the rope wraps around one of his legs. In a closeup shot, the rope is wrapped around both his legs.

When the person's head falls off, blood completely covers their face. When the head is shown on the ground, a patch of the head isn't covered with blood.

In the wide shots of the person struggling with the creature feeding on his neck, the rock is jagged and uneven. in the closeup shots, the rock is flat, like the concrete wall of a building.

After Burt and Maurine's sonar device's antenna is broken by a rat, the wide shots show the device without its antenna, however a subsequent closeup shot of the device in Burt's hand still shows the antenna.

When Roy and Thelma arrive back in the supposedly deserted city, cars and people can be seen in the background of one shot.

When one of the characters have their eye bitten out, the rocks around her are clearly shaking.

When Cliff shines the light in Jill's eye, her eyelid is moving.

The film re-uses a closeup shot of a radio in a character's hand for several different devices throughout the film. This includes Cliff's handheld transceiver and the sonar device used by Burt and Maurine.

When Thelma shakes Cliff, her helmet falls off, but makes no sound as it hits the ground.

Part of a camera is visible in the car mirror when Roy lights a cigarette and Thelma is running onto the beach.

When the speleologists are walking about in the cave, a camera behind them is clearly visible.

A rope probably used to pull down the fake head is seen falling a small distance to the ground next to the head.

During the opening driving sequence Roy's truck is heading in the wrong direction to get to downtown San Diego on the Coronado Bridge.

When Roy climbs down to inspect Jill, the tip of the microphone is visible in the top right hand side.