But John has told us in v. 15 that Jesus went off to be alone and he has told us of the pressures that would have sent the Lord to his knees and to his Father in heaven in prayer. Matthew and Mark tell us that it was a contrary wind. The surface of the Sea lies some six hundred feet below sea level and up to two thousand feet below the summits of the surrounding hills. The difference in temperature at the top and bottom of the hills is considerable and causes air to rush downhill through the ravines that lead to the water.
Storms can come quickly and can be quite fierce for a lake as small as the Sea of Galilee is.
At its greatest width the Sea of Galilee is 61 stadia in length, so they were somewhere in the middle of the lake. It is not clear whether we are to understand v. 21 to mean that there was a second miraculous effect in the speed with which the boat came to land after the Lord was brought into it, or if John simply means that after Jesus got into the boat the wind died down and the sea became calm, as Mark tells us happened, and then quickly they brought the boat to shore. It was night and you remember that darkness, in the Bible, is a symbol of evil, ignorance, trouble, and sorrow. The Bible speaks of the powers of darkness. And, in an age before electric lights, no wonder.