Reviewed on 3/5/2014...
An excellent movie, irrevocably ruined by a single, huge, and ridiculous plot hole at its very end. I do not recommend this movie. Instead, I recommend the Issac Asimov book which addresses this plot hole.
Movies rarely reflect reality, and that's OK. We're looking to be entertained, and if the screenplay is somewhat (or even completely) unbelievable, who cares, as long as the movie is good?
A movie must (in general) not leave any loose ends for the audience to say "but what about ...". In Pulp Fiction, we never got to see what was inside the briefcase, but what was in the briefcase wasn't integral to the plot. That kind of "but what about ..." loose end only sparks speculation. The same thing applies to the 1960's TV series "The Prisoner". There are a ton of holes and unanswered questions, but who cares? Debate continues to this day about what 'this' meant, how much significance 'that' had, etc. The worst you can say is that "The Prisoner" was consistent with its inconsistencies. It was highly entertaining!
In 1966's Fantastic Voyage, a genius scientist suffers a brain injury thanks to an attack by "the bad guys" (presumably the cold-war USSR) and is unable to pass his knowledge along to "the good guys" (presumably the cold-war USA). A conventional operation will not work. A crew and small submarine must be miniaturized and inserted into the scientist's blood stream to operate 'from inside'. But they have to do it in 60 minutes - that's the maximum amount of time miniaturization can take effect (and a solution to that problem is what the genius scientist knows, by the way).
So the crew is miniaturized and inserted in the blood stream. Things go wrong, of course, and the crew goes on adventures in several parts of the body they never anticipated going to. The special effects suffer due to 1960's technology, but it's still good stuff.
As the 60 minutes runs out, all crew members but one are outside of the submarine (the one still inside the sub being a traitor). The operation is a success. The crew and sub must get out of the body before they de-miniaturize and turn the scientist's head into a mass of jelly (and they themselves will surely die in the process).
So here comes the glaring plot hole ... all the "good guy" crew get out via the eye - they're like a spec of dirt in a teardrop as they are placed on a microscope slide. The slide is rushed into another room, the "good guy" crew slowly de-miniaturizes, and they're all safe. Relief is obvious on the faces of the people who were overseeing the operation from the outside. They shake hands with the crew, everyone is all smiles, and the credits roll.
"But what about ..."!!! The sub (and the traitor crewman, for that matter) never got out of the scientist's body. In the next room, his head is a mass of jelly, exploded by the de-miniaturizing sub! The "good guy" crew may have survived, but the operation was obviously a failure. The smiles and handshakes make no sense.