If Jonah knew he was the cause of the storm, then why not just jump off the ship, instead of requiring the sailors to throw him over?
because of this:
2 Kings 6:1-7
And the sons of the prophets said to Elisha,
"See now, the place where we dwell with you is too small for us. Please, let us go to the Jordan, and let every man take a beam from there, and let us make there a place where we may dwell."
So he answered,
"Go."
Then one said,
"Please consent to go with your servants."
And he answered,
"I will go."
So he went with them. And when they came to the Jordan, they cut down trees. But as one was cutting down a tree, the iron ax head fell into the water; and he cried out and said,
"Alas, master! For it was borrowed."
So the man of God said,
"Where did it fall?"
And he showed him the place. So he cut off a stick, and threw it in there; and he made the iron float. Therefore he said,
"Pick it up for yourself."
So he reached out his hand and took it.