"... there is yet another point to be made. We recall that when Jonah confesses his error to the horrified sailors, he tells them that 'the Lord, god of Heaven, is whom I worship' (verse 9). In annotating that statement above, I pointed out that locating 'et-YHWH at the head of the clause gives God's name special attention. Despite this rhetorical flourish, the sailors did not seem totally convinced then by Jonah's words. Now, however, an eerily instantaneous calm follows Jonah's seaward plunge. By shaping the clause this time to end in 'et-YHWH, the narrator is finally granting the sailors their own recognition of God's greatness. The sailors now understand everything about God and divine power. They demonstrate this recognition by two activities, a sacrifice and a vow. The first of these measures troubled ancient exegetes, who were aware that, except in a couple of instances in which it is read metaphorically or ironically, the G of the verb zabah always refers to the slaughter of animals. Where did the sailors get the victims, especially after they had denuded the ship to keep it afloat? Moreover, could sailors so recently 'converted' to the true God risk losing it all by offering sacrifices outside of the Jerusalem Temple? Jerome resolves such difficulties with the comment (comparing Psalm 50:14 with Hosea 14:3) ..."

Sasson, Jack M. Jonah: A New Translation with Introduction, Commentary, and Interpretation (p. 138) Doubleday, 1990