Goofs

The beast has a snake-like forked tongue in some shots but a normal one in others.

When Prof. Nesbitt, in Lee Hunter's apartment, is going over sketches of different dinosaurs, Lee hands him a sketch; there is a quick glance of it as he takes it from her. When the camera then shows the sketch he is holding and pointing to, it is not the sketch that Lee had handed him a moment before.

When the fishing vessel "Fortune" is attacked by the Beast, it is shown moving from right to left. In the wheelhouse, Jacob looks to the left, which would be port, and reacts in horror as he sees the Beast rise up out of the water. The Beast then pounces right away, crushing the wheelhouse roof down, then the shot switches to the exterior. The ship is still moving right to left, but the Beast is shown attacking from the starboard side of the ship, when it should have been attacking off the port, where Jacob had just seen it.

When the hero and the lady scientist are looking at the drawings of the dinosaur in her living room, the sandwich and coffee cup keep appearing and disappearing.

Shortly after Nesbitt has awakened in the hospital he notices something in the newspaper. This something is below the fold, but when he shows it to the nurse, it is above the fold.

One fathom equals six feet. The beast must have come from about 23 miles down. The sea is only seven miles deep at its deepest!

When the four men are traveling aboard the half-track near the beginning, the distant mountains in the background are moving past very rapidly. For that to occur, at that rate, the half-track would need to be moving at 1,000 mph or greater. It would have been more realistic if the background mountains had remained completely stationary, while the half-track moved forward.

The aircraft shown in the beginning approaching the bomb drop is a Douglas DC-3S. The speed announced by the person tracking the plane's progress is 360 mph. The top speed of the DC3S was 250 mph. It also is a cargo plane and has neither a bomb rack nor anywhere near the range quoted in the movie.

Tom Nesbitt fears he will go to a "psychopathic" hospital. A psychopathic hospital, if It exists, would be for murderers and other violent criminals. He likely meant "psychiatric" hospital.

The monster is reported to be in "Manhattan Beach", and when the authorities arrive there they discover it in a big amusement park. This park is actually a replica of that at Coney Island, which is actually several miles from Manhattan Beach in Brooklyn; there's never been an amusement park such as this in Manhattan Beach.

During the diving bell sequence, there is a fight between an octopus and a shark. Early on, as the octopus tries to get away, it can be seen that it is using the glass wall of its aquarium to move itself.

Shortly after the beast comes ashore in New York, he is shown emerging onto a street from a side street, and pausing. Behind him are a number of cars and pedestrians who continue to drive or walk casually, which they would certainly not be doing if a huge prehistoric monster had just appeared less than a block away.

The roller coaster is actually in Long Beach, CA, not New York City. This is revealed when the two men climb into the cars. A sign which says "Cyclone Racer" can be seen. New York's coaster is just "Cyclone". Also, in one of the outdoor shots, the "Jackrabbit Racer", which is also in Long Beach, can be seen.

Before the attack on the lighthouse, one of the lighthouse keepers is shown playing a concertina. His fingers do not move on the keyboard; he is not actually playing it, just squeezing it in and out.

At the end of the underwater struggle between the octopus and the shark, a segment of the fight is run and then played in reverse to stretch the scene out. The shark twists, pauses, and then reverses its movements.

When they check the outposts after the bomb blast from a non-bomber, they go directly to outpost sixteen. Apparently one, through fifteen, are not important, but seventeen and eighteen are, both of which are in opposite directions.

Nesbitt, trying to persuade Prof. Elson to consider his story, says that Galileo claimed the world is round. That was accepted in Galileo's time. His claim was that the earth moves around the sun.

While looking at the beast from the diving bell, Professor Elson refers to it as "paleolithic survival". The Paleolithic period (aka the Stone Age) goes back only as far as 2.6 million years, but the professor also claimed that the beast would be at least 100 million years old.

Prof. Nesbitt and Lee Hunter don't look through the pictures of dinosaurs and fossils in a very scientific manner. They would have saved considerable time if they had narrowed the choices before going through hundreds of different dinosaurs, the vast majority of which could have been skipped based on three basic criteria: biped or quadruped, size, and basic body shape. A physicist might not have thought of this, but the assistant to a professional paleontologist should have.

When Prof Nesbitt is being interviewed in the hospital shortly after the start of the movie, he is being told that sea monsters do not exist and the interviewer mentions Loch Lomond as an example. He obviously means the Loch Ness monster. Given that, he is further erroneous in stating that it had never been photographed, as one of the most famous photos of "Nessie" was taken in the 1930s.