Job is sent by God to Ninevah, which is in present day Iraq near Mosul. It was the largest city in the world for a long time. But because it was oppressive, Job did not want to be sent there, lest they repent. He wanted them to be judged, so instead of going, he went west. The Leviathan was sent to take him back toward the direction he was told to go. Think of it as a taxi service. The point is, if you are disobedient, God will change your circumstances to get your obedience. In a general sense, our circumstances are sometimes indicators of the direction God wants us to go.
Cool name and means "wreath" or gathered into folds, from Heb, liw-ya-than. This occurs six times in the Bible. Seems to indicate a form of aquatic creature of great proportions. possibly a whale of sorts. In Job 41:1-34 the description fits more likely to a crocodile as in the Nile crocs and the sea mentioned is the Nile. It's as betty says above. NWT more on (jw.org)