He said to them, "Take me up, and throw me into the sea. Then the sea will be calm for you; for I know that because of me this great tempest is on you."
Why did Jonah not end his own life by jumping overboard? I suspect that he did not have the courage to do so. Obviously it took considerable courage to advise the sailors to throw him into the sea where he must have expected to drown, but suicide takes even more courage.