And about the fourth watch of the night he came to them, walking on the sea. He meant to pass by them, but when they saw him walking on the sea they thought it was a ghost, and cried out, for they all saw him and were terrified. But immediately he spoke to them and said, “Take heart; it is I. Do not be afraid.” And he got into the boat with them, and the wind ceased. And they were utterly astounded, for they did not understand about the loaves, but their hearts were hardened.
Mark 6:48–52 ESV
The disciples wondered who is Jesus? He can feed more than 5000 people, but is he just a miracle worker? Or is he a good prophet? No, more than that, Jesus is God. For only God can walk on water!