Jonah 1: 17: Now the LORD had prepared a great fish to swallow up Jonah. And Jonah was in the belly of the fish three days and three nights.
Jonah 2: 10: And the LORD spake unto the fish, and it vomited out Jonah upon the dry land.
When Jonah disobeyed the LORD and instead went on a cruise to Tarshish rather than go to Nineveh and warn them of impending judgment, his whole life began to go downward, for the Bible tells us that he went down to Joppa (Jonah 1: 3), then he went down into the ship (Jonah 1: 3), then he went down into the ocean (Jonah 1: 15), and lastly, he went down into the fish (Jonah 1: 17). This fish was specially created by God to swallow up His prophet, and Jonah would spend three days in its belly whilst unknowingly enroute to the destination he had formerly tried to run from.
After three days, this special fish that predated the modern submarine, eventually surfaced near the coastline and unloaded its human cargo in a most unseeming fashion, vomiting poor Jonah upon the shore, all covered in stinking seaweed and other undigested seafood. Now with an attitude that was a little more willing to obey, Jonah then made his way to the city of Nineveh and declared the urgent message God had given to him.
Upon hearing Jonah’s message and learning that he had been sent to them via the transportation of a fish, the Ninevites readily repented and dramatically changed their ways. The reason for this sudden and most unexpected turnabout of their hearts is because the Ninevites worshipped the fish-god Dagon, thus when they heard that this foreign prophet had stepped out from their ocean god, they became very receptive to all that he had to say and quickly heeded his warning and repented of their wickedness.