It's the story of the two soundest sleepers in the whole Bible - Jonah and Jesus. 

A lot that happens in Jonah's life is a symbol for what would happen in the life of Christ. But there is one major difference. And that difference is displayed on a boat and in a storm in which both Jonah and Jesus were able to sleep straight through. Had it not been for their eventual responses to being woken up in the storm, the crew on the ship might have perished.