For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I
The old man hasn’t caught a fish in eighty-four days, which is a decidedly bad thing.
Act II
The old man hooks, battles with, and ultimately kills a really, really, ridiculously big marlin.
Act III
Sharks eat the fish and the old man admits he has been defeated. But has he? He falls asleep, dreaming about lions.