Why does Pi say he turned to God after leaving the island?

Pi turns to God for relief from his suffering.... for sustenance and hope.

High calls low and low calls high. I tell you, if you were in such dire straits as I was, you too would elevate your thoughts. The lower you are, the higher your mind will want to soar. It was natural that, bereft and desperate as I was, in the throes of unremitting suffering, I should turn to God.