Time to start the monumental deconstruction work: first sentence.

"He was an old man who fished alone in a skiff in the Gulf Steam and he had gone eighty-four days now without taking a fish."

Plot and Character:
One critical thing a writer can do to capture the reader's interest immediately is to start the narrative with a dramatic scene and simultaneously introduce the human aspect. Arguably, Hemingway does this with the first compound-complex sentence,  even if it is recounting the recent past.

"He was an old man" instantly forces the reader to picture an old man, perhaps one in their life, and leads the reader to immediately sympathize with the character.

"had gone eighty-four days" deepens the plot, allowing the reader to fill in the previous time gap with their own imaginings of the old man returning each day without a catch, reinforcing the sympathetic element and introducing an anxiety into the reader's mind. This is emotional writing and it's essential the writer infuse every paragraph with emotion by using emotional concepts like loneliness and isolation or sensory description originating from our five senses.

Because psychological findings indicate the mind tends to put belief in odd vs rounded up or down numbers, the unusual number of days mentioned makes the tale more convincing.

Style:
"fished alone in a skiff in the Gulf Stream"  accomplishes five artistic goals;

• provides a three part description that appeals to the mind's love of threes.
• it projects rhythm using a two, three, and four syllable beat.
• it uses a three camera perspective technique; the description moves from the close up of the man with the word "alone",  to panning back and including the boat,  and finally to the image of the vast Gulf Stream surrounding the tiny and fragile skiff.
• it provides deeper diction and variegation than expected; replacing "boat" with "skiff",  "ocean" with "Gulf Stream" and later "catching" with "taking"
• uses three adverbs to modify "fished": alone (how), in a skiff (where), in the Gulf Stream (where).  Note Hemingway could have added more adverbs to answer the when, why, condition, concession, comparison/contrast, frequency of "fished"; however, this would disrupt the rule of three and erode the mystery of the man. Here it is using showing not telling writing so the reader can speculate about the man's predicament, yet another important factor required in capturing the interest of the reader.

Setting:
"Fished alone in a skiff in the Gulf Stream" generates a tangible sense of loneliness, precariousness, and sympathy with regard to the character.

Syntax:

It starts with a compound complex sentence: one independent clause (he was an old man) with an attached adjectival clause (who fished alone in a skiff in the Gulf Steam)  linked by a coordinate conjunction (and) to another independent clause (he had gone eight-four days now without taking a fish)

Parts of speech skeleton: pronoun, state of being verb, adjective, adjective, noun, pronoun, past participle verb, adverb, preposition, adjective noun, preposition, adjective, noun, conjunction, pronoun, state of being verb, adjective, noun, adverb, preposition, present participle verb, adjective, noun.


Phrases:

• Adverbial phrases: "in a skiff" and "in the Gulf Stream" both modifying the verb "fished";  "without taking a fish" modifying "had gone"