1:4 - The Lord hurled a great wind on the sea and there was a great storm on the sea so that the ship was about to break up.
The battle of wills is engaged as the Lord starts His discipline in Jonah's life. Note that the Lord brought turmoil only to a certain point - the ship did not break up. God's control of the elements would not have surprised the original audience.
This is God's first confrontation. He brings a general call to turn back which affects everyone around Jonah.
1:5 - Then the sailors became afraid and every man cried to his god, and they threw the cargo which was in the ship into the sea to lighten it for them. But Jonah had gone below into the hold of the ship, lain down and fallen sound asleep.
The original audience may have laughed at the sailors' cries to dead gods, knowing that there was no hope for them. Note that the sailors were so afraid of this storm that they jettisoned their livelihood, the cargo; also, note that while we don't know anything about the sailors, we could assume that this was not a crew that was inexperienced. I'm sure they had encountered storms before, but of course, this one was different.
Contrast Jonah's actions with the sailors; he is sound asleep (not just asleep, but sound asleep), which is just about the polar opposite of the frantic, fearful activity of the crew. It may have crossed his mind that should he perish at sea, he wouldn't have to go to Nineveh. This attitude is reflected in Jonah's statement in v. 12.
This verse serves to record Jonah's reaction to God's general call to repentance in v.4. He refuses to turn back. Astute original audience readers would recognize the same call in their own lives; they may have ignored it, but still have recognized it.
1:6 - So the captain approached him and said, “How is it that you are sleeping? Get up, call on your god. Perhaps your god will be concerned about us so that we will not perish.”
Here is God's second confrontation: confrontation by one. The pagan captain rebukes the man of God and calls him to pray! There is no indication that Jonah did pray; in fact, because the storm continues, I think we can rightly assume that Jonah did not pray.
God brings judgment on the whole ship in order to turn around Jonah. Israel would recognize the same pattern in their lives as God had brought foreign armies as well as various plagues to discipline the whole nation.
By using the pagan captain to confront the prophet, God would further engender the original audiences' allegiance to Jonah. "How dare that filthy Gentile talk that way to one of God's chosen people! He is praying to a dead god, while we serve the living God!"