The Jonah prayed to the Lord his God from the belly of the fish
This is the first time in the book of Jonah that Jonah speaks or prays to God. As far as we know, he didn’t pray when he received God’s command and didn’t like it, he didn’t pray in the storm - he would rather die than cry out to God at that point. Did he even pray when the fish swallowed him? Has it taken the 3 days/nights to get him to this point?
His prayer is described as being to the Lord his God - although Jonah has claimed allegiance to God in chapter 1, there hasn’t been much so far to suggest the personal relationship indicated here.
A fish belly is a random location for prayer! Jonah has hit rock bottom and then cries out to God. How often do we find that our prayer life comes alive when we’re at rock bottom and dwindles when things seem to be going well? It is God’s grace to put us at rock bottom if the result is that we start crying out to the Lord our God.