The sea ceased from its raging after Jonah was thrown in Jonah 1:15. The sailors then feared the LORD exceedingly and offered a sacrifice and made vows Jonah 1:16.
This unit concludes the shipboard crisis in Jonah 1. Just before it, Jonah identifies himself as fleeing yahweh and presents being thrown overboard as the means by which the sea will quiet.
This passage matters because it ties the detail to the larger movement of the book, keeping the answer connected to context rather than isolated wording.
A careful answer keeps the immediate passage, the book's argument, and the whole-Bible storyline together, so the question is answered in context instead of as a detached idea.
Start with Jonah 1:15, then read the surrounding section so the answer stays connected to the passage's flow.
15So they took up Jonah, and threw him into the sea; and the sea ceased its raging.