In Prep school we learned that Jonah was in the belly of the big fish for 3 days and 3 nights. God placed him there so Jonah could examine his thoughts and actions, then repent (admit he sinned and make the decision to obey God).
The kids in prep school gave examples of how to seal a door forever using hammer, nails, super glue, and cement! The sealing ministry of the Holy Spirit is way stronger than all of that… times infinity!