Before we start, here is John 6:16-21:

16 Now when evening came, His disciples went down to the sea, 17 got into the boat, and went over the sea toward Capernaum. And it was already dark, and Jesus had not come to them. 18 Then the sea arose because a great wind was blowing. 19 So when they had rowed about three or four miles, they saw Jesus walking on the sea and drawing near the boat; and they were afraid. 20 But He said to them, “It is I; do not be afraid.” 21 Then they willingly received Him into the boat, and immediately the boat was at the land where they were going. (John 6:16-21, New King James Version)