What is the effect of juxtaposing the naval officer in his uniform with the bloody, sweaty Ralph who can barely remember who he is?

The Navel Officer represents the adult world an hence brings a definite stop to the story. He is Golding's deus ex machine or "God in the Machine". The Navel officer literally comes out of nowhere and ends Golding's social experiment. The Naval officer is everything the boys should have been but weren't. The officer represents the height of civilization; he is clean, disciplined and bewildered at the spectacle in front of him. Ralph, and the other boys, are wild, dirty and caught in their own world of savage destruction. The scene is like a reverse mirror. It shows the result (sailor) of a regulated world of learning, rules and maturity. The filthy boys represent a world that is unregulated where human nature is left to develop as it pleases, perhaps as it really is.