"So they asked him, 'Tell us, who is responsible for making all this trouble for us? What do you do? Where do you come from? What is your country? From what people are you?' He answered, 'I am a Hebrew and I worship the Lord, the God of heaven, who made the sea and the land.' This terrified them and they asked, 'What have you done?' (They knew he was running away from the Lord, because he had already told them so.)" NIV translation
Now that they know which man has caused the chaos to be on them, the sailors start to ask questions of Jonah. When he explained that he worshiped the Creator of everything including the sea, they were terrified as they were witnessing the power of God. They could see that God was not so happy with him so they asked him what he had done. God corrects His children and the sailors understood that this storm was because of his disobedience. God does not want us to sin (be out of His will) but he loves us enough to allow the storms to get our attention back to Him.
"The sea was getting rougher and rougher. So they asked him, 'What should we do to you to make the sea calm down for us?' 'Pick me up and throw me into the sea,' he replied, 'and it will become calm. I know that it is my fault that this great storm has come upon you.' Instead, the men did their best to row back to land. But they could not, for the sea grew even wilder than before." NIV translation
God turned up the heat by increasing the storm. Now that the sailors know the source of the problem, they ask for a solution. When they heard the answer, they did not like God's plan and so chose to try something else (rowing back to land). So, God had to turn up the heat and make it even worse for them. We may look at the sailors and say how foolish they were but don't we act in much the same way?
God has revealed His plan to save men yet all too many choose to try and find their own way. So, God may turn up the heat. The same is true for those who have accepted His plan of salvation and are now called His children. We still may not like the plan He has for our lives in Christ and may not want to obey and do what He tells us. Once again, God may turn up the heat but we must remember that God does it for our own good and He sees the whole picture while most of the time we only see pieces.
"Then they cried to the Lord, 'O Lord, please do not let us die for taking this man's life. Do not hold us accountable for killing an innocent man, for you, O Lord, have done as you pleased.'" NIV translation
An awesome thing came out of this storm and that is described in this verse. The sailors "cried out to the Lord" instead of crying out to their own god as in verse 4. They admit that there is only one God and that He is in control even of the storm.