My response to the question of whether to believe it or not, is to believe it. You, like I, may always have doubts about what things really happened back then, and, then also, why would anyone write such a fantastic story like this? The late Fr. Benedict Groeschel (who was seen on EWTN) would answer by saying “I wasn’t there.”
Surely you are referring to the episode depicted there of Jonah surviving in the belly of the fish.
But, recall, Jesus referred to that very incident – not skeptically – but to the contrary that Jesus would also give them that “sign,” referring to His resurrection from the dead. So, are you with Jesus, or against Jesus?
The book of Jonah is short, and it is read in the synagogues every year, in its entirety, on the holiest day of the Jewish calendar, Yom Kippur, the day of atonement. Now, why would that be? What is the BIG story of the book of Jonah?
In and of itself, it is a “story” of Jonah (a prophet) being sent to preach repentance to the people of Nineveh. And, low and behold, much to Jonah’s disgust, the people DO repent and the city is saved from God’s wrath of destruction. So, to the Jews – God’s chosen people – this is a proof that they too should learn the lesson of repentance, and they remind themselves of, if not every day of their lives, then at least once a year on this holiest of days, that their atonement for sin comes with their sincere repentance.
THAT is something you ought to believe. (The Bible does not end with the scroll of Jonah, of course, we cannot atone for our sins, but Jesus our Savior atoned for our sins on the cross – that was the fulfillment of the Old Testament “day of atonement.”)
Whether that part of the story about the fish is literally true (and some people think it is plausible), the part about the repentance of Nineveh is actually harder to believe, and Jonah camps outside the city, at a distance, just waiting for the spectacle of God’s destruction of the city, which never comes. Jonah is skeptical throughout the book of Jonah.
So, (how many times have I said “so”?) the scroll of Jonah is not primarily about a fish, and not primarily about the repentance of a city of gentiles, it is about Jonah. And, what do we learn about Jonah? Well, maybe, that we ourselves should not be skeptical, reluctant prophets of God’s words, but we should be faithful, even eager prophets of God’s word.