Final answer:
The situational irony in 'The Colomber' happens when the protagonist avoids the colomber his entire life, only to learn it wanted to give him a pearl of happiness, rather than harm him.
Step-by-step explanation:
The situational irony in "The Colomber" by Dino Buzzati occurs when the protagonist, Stefano Roi, spends his life running away from the colomber (a sea monster), believing it is his doom, only to discover upon facing it at the end of his life that the creature has been trying to give him a pearl that grants eternal happiness. This is ironic because Stefano's fear of the colomber leads him to a life of avoidance and trepidation, contrasting the peace and good fortune the colomber was actually intending to bring him. The irony lies in the unexpected reversal of roles, as the perceived threat is, in reality, a bearer of a great gift.