Paul Berlin is a soldier on his first tour of duty in the Vietnam War. Shortly before the story begins, another soldier in Paul's platoon had died after stepping on a mine, and then having a heart attack. Paul reflects on the infectious nature of the fear which killed Billy, and consoles himself by thinking that once the platoon reaches the sea, he will no longer be afraid. Yet, the more Paul thinks about Billy's death, and how ridiculous and nonsensical it is, the more the fear of that senselessness grips him.
At the end of the story, the final line reads,
But even when he smelled salt and heard the sea, he could not stop being afraid.
implying that the platoon did reach the sea, but it did nothing to calm Paul; he is still afraid, and he probably will be for a long time, if not forever.