In "The Open Boat," after the others have dropped off to sleep, the correspondent sees "a long, loud swishing astern of the boat, and a gleaming trail of phosporescence, like a blue flame, was furrowed on the black waters. It might have been made by a monstrous knife." What had the correspondent seen?

Fin of a shark

Explanation:

The Open Boat is written by Stephen Crane. It is is an intense short story that is subjected on the real life story of the writer. The story starts from a voyage ship, it was going towards Cuba but the ship sank due to water turbulence near Florida. In the story the author had narrated the experiences that he felt on his way to Cuba and one of that has been mentioned in question statement

What had the correspondent seen?

The correspondent had seen the incursions of the "wave," which Crane in his narration referred to the vicissitudes of life.

The narrator refers to "a long, loud swishing astern of the boat, and a gleaming trail of phosporescence, like a blue flame, was furrowed on the black waters. It might have been made by a monstrous knife," as the problems of life shaping the destines of men.

Explanation:

The Wave

A ceaseless presence in the story and constant nuisance to the b oat occupants, the ocean waves suggest both the forces of nature and uncontrollability of life. At the beginning of the story, the narrator presents the waves as the men's primary concern, the thing they must master if they are to survive the shipwreck. In this sense, the waves resemble the ever-changing demands of the present, the part of life that demands the most attention but allows for the least reflection.

Crane seems to imply that because the men cannot control the waves' ebb and flow, man in general cannot affect the outcomes of his life and can hope only to respond constructively to what he encounters. Just as the waves are constantly changing, becoming sometimes violent and sometimes favorable, the pressures in man's life will continue to jostle his progress toward whatever he seeks.