Prophet Yūnus ﷺ (Jonah) was sent to the people of Nineveh (in modern-day Iraq). After years of preaching with little success, he became frustrated and left his people without Allah's explicit permission — a lapse for a prophet of his station.
He boarded a ship, which was struck by a violent storm. The sailors drew lots to see who should be thrown overboard — it fell to Yūnus ﷺ. He was swallowed by an enormous whale. In the darkness of the whale's belly, in the depths of the ocean, he made the most famous supplication of any prophet:
After his sincere repentance, Allah commanded the whale to release him on the shore. He was ill and weak — a plant (gourd vine) grew over him for shade and recovery. Allah then sent him back to Nineveh — and this time, 100,000 people believed, one of the greatest mass acceptances in prophetic history.