פּירוש אויף יונה 1:3

to flee to Tarshish—I.e, to a sea named Tarshish, which is outside the Holy Land. He said, “I will flee to the sea, for the Shechinah does not rest outside the Holy Land.” Said the Holy One, blessed be He, to him, “By your life, I have messengers like you to send after you and fetch you from there.” This is illustrated by an allegory of a priest’s slave who fled from his master and entered a cemetery [making it impossible for his master to retrieve him]. His master said to him, “I have slaves like you to send after you and fetch you from there.” Now what did Jonah see that he did not wish to go to Nineveh? He said, “The gentiles are quick to repent. Should I prophesy to them and they repent, I will be found condemning Israel, who do not heed the words of the prophets.” [from Mechilta, Exodus 12:1]

He went and fled to Jaffa: The gaon said that Tarshish is Tarsus. But Rabbi Mevaser says that it is Tunis in Africa.

The Questions — Why did Jonah flee to Tarshish? If [he fled] so that the word of Hashem would not reach him, then, behold, Hashem had already commanded him [to go to Nineveh] and he refused to go on the mission. What difference does it make if he refuses once or if he refuses twice? And why did he flee to the sea and not to the desert and from there to chutz la’aretz [‘outside the Holy Land’]? For, behold, the sea is suitable for prophecy, as it is written that God appeared to Ezekiel in chutz la’aretz because he was in a place of water (Ezekiel 1:3). And the phrase ‘ba’ah Tarshish,’ ‘arriving Tarshish,’ [appears] incorrect, for it should have said, 'holechet Tarshish,' ‘going [to] Tarshish.’

and he paid its hire—He paid its hire in advance; although it is not customary for those embarking upon the sea to pay the hire of the ship until they leave, he paid in advance. [Pirké d’Rabbi Eliezer, ch. 10; Tanhuma, Vayikra 8].