Christ's miracle of walking on the water (Matthew 14:22-33; Mark 6:45-52; John 6:15-21) took place soon after feeding the 5,000. The next day He preached a sermon in the synagogue that turned their rejoicing into near total rejection—almost all but the twelve disciples left Him. A representative of God must not trust in human praise nor withhold the truth to try to please people. Instead, as a true witness, he must preach God's truth regardless of the world's disapproval.
Later, Jesus told His disciples to set out in their boat for the western shore of the Sea of Galilee. At three hours after midnight, straining at the oars against the storm, they were still only halfway across the lake. In a contrary wind and tossed by the waves, the disciples did not realize that Jesus was fully aware of their difficulty. They were about to learn of His sympathy and willingness to come to their aid. He approached the distressed disciples in an entirely unexpected way, by walking on the turbulent sea as if it were stable as rock.
Clearly, He had been praying for and watching out for them while on the mountain, but when He passed near them, they did not recognize their Savior. The night was extremely black in the storm, and their nerves were on edge with fear. Under these conditions, they thought He was a spirit, an ominous apparition of some kind. But He encouraged them immediately with familiar reassurance: "Be of good cheer! It is I; do not be afraid." Later in their lives during times of anxiety, this moment probably came to mind as a lesson deeply received and continually comforting.
Martin G. Collins
The Miracles of Jesus Christ: Walking on the Water (Part One)