Factual error: Even if the white blood cells will attack and destroy the sub and the body of doctor Martin the atoms would still remain and take normal size after the critical 1 hour is up. This would also apply for the laser gun which they forgot or left behind on purpose.
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When a crew member of the miniaturised submarine is eaten by the blood cells, the fact that his atoms will return to full size at the same time as the rest of the crew and the submarine (which provides the suspense, such as it is) is completely ignored. See more...
Fantastic Voyage mistakes
Other: During the miniaturizing scene the technicians controlling the forklift wore sterile gloves, the nurses assembling the syringe did not.
Plot hole: When a crew member of the miniaturised submarine is eaten by the blood cells, the fact that his atoms will return to full size at the same time as the rest of the crew and the submarine (which provides the suspense, such as it is) is completely ignored.