"He (Jesus) answered, "A wicked and adulterous generation asks for a miraculous sign! But none will be given it except the sign of the prophet Jonah. For as Jonah was three days and three nights in the belly of a huge fish, so the Son of Man will be three days and three nights in the heart of the earth." Matthew 12:39-40
"Three days and three nights in a fish's belly? Are you kidding me?"
You have to admit the story of Jonah sounds a bit far-fetched. He ran from God's will and was thrown overboard during a vicious storm. When he was thrown overboard he was swallowed by a "great fish" where he remained for three days and nights. That unfortunate event was enough to convince him to obey God. Once he made that decision, the gigantic fish spit him up onto dry land - exactly where he needed to be.
Wow! Happens all the time, right?
I believe it because I believe God's Word and I know God is well able to do something like this. In this case, I believe it because Jesus refers to the story of Jonah as a true story. Even his adversaries believed the story of Jonah even though they didn't believe Jesus.
A second objection that skeptics offer to challenge the inerrancy of the Scriptures is this one, "Could Jonah REALLY have survived in the belly of a fish?"
Actually, yes! There a several reports of mariners in the modern era who have been swallowed by whales yet survived the ordeal. It's been documented that there would be enough oxygen within the whale's body for a human to survive for three days. Those are the natural facts, but Jonah's survival was supernatural!
Those who ridicule the story of Jonah and point to it as evidence to discredit the Bible offer no objective or logical argument. Neither do they offer any contrary evidence. All they bring to the table is their anti-supernatural bias. From that standpoint alone, our argument is just as valid as theirs because we have as much right to an opinion as they do.
However, we do have some evidence to support our claims. Chief among the evidence is the fact that Jesus twice is documented as referring to Jonah (Matthew 12 and Luke 11). He is not pointing to Jonah as a fairy-tale, but as fact.
If you don't take the supernatural out of play, you can easily believe that God could create a "great fish" especially designed for the task, He could put the fish where it needed to be and turn it into transportation to deliver to the shore near Nineveh.
God created all the other sea creatures, He could certainly have done this.
Incidentally, the miracle of Jonah and the fish was the next to last miracle that happened in the Old Testament.
What was the last miracle?
The final miracle of the Old Testament was what happened when Jonah went to the wicked city of Nineveh and preached - the entire city repented and was converted! Talk about supernatural!
It is easier to prove that the Jonah event did happen than it is to prove otherwise! So, if someone tells you this sounds "fishy" - don't take the bait!