From the belly of the fish, Jonah recognises that God is saving him from his situation and God is his protector. Jonah recognises that anything that people are reliant on other than God is a ‘vain idol’ which will fail them. In this Jonah is repenting of his actions and confessing that God is the sovereign source of salvation.
The second chapter of this story shows us that idols will never satisfy us and only by keeping Jesus in his rightful place will we experience life.