Fantastic Voyage (1966)

A group of medics (Stephen Boyd, Raquel Welch, William Redfield, Arthur Kennedy and Donald Pleasence) and a submarine are miniaturised and injected into the bloodstream of a top Czech scientist, who was shot while defecting, in order to carry out delicate, life-saving surgery. Travelling though his body is hazardous, but far more dangerous is the suspicion that one of them is a traitor. They race against time to perform the surgery and escape from the body before they return to their full size. The film won Oscars for Best Cinematography and Best Editing.