A little further digging and I discovered Asimov was invited to write the novelization of the existing script before the the film was due to be released. He agreed, but only if he was allowed to fix the scientific holes. That was OK, but his fixes did not make it into the film as they had already started shooting.

The fixes included, for example, having the submarine come out of the patient’s body though his tear duct and not get left behind as in the film. Even though the film makes it clear the submarine is “eaten” by white blood cells, Asimov pointed out that the miniaturised molecules of which the submarine was composed would, logically, also return to their original size after the 60 minute limit was passed, with fatal consequences for the patient.

Anyway, delays in the filming and Asimov’s famous writing speed (very very much greater than yours truly) meant that the book was published before the film was released, so it looked as though the film was a travesty of Asimov’s book, rather than Asimov book being a correction of the film.

Not many people know that! 🙂