7 Now the fourth watch of the night, is the end of the night; for each watch consists of three hours. It signifies then, that now in the end of the world the Lord has come to help, and is seen to walk upon the waters. For though this ship be tossed about by the storms of temptations, yet she sees her Glorified God walking above all the swellings of the sea; that is, above all the principalities of this world. For before it was said by an expression suited to the time of His Passion, when according to the flesh He showed forth an example of humility, that the waves of the sea vainly raged against Him, to which He yielded voluntarily for our sakes, that that prophecy, “I have come into the depths of the sea, and the floods overflow Me,” might be fulfilled.
For He did not repel the false witnesses, nor the savage shout of those that said, “Let Him be crucified.” He did not by His power repress the savage hearts and words of those furious men, but in patience endured them all. They did unto Him whatsoever they listed; because He “became obedient to death, even the death of the Cross.” But after that He was risen from the dead, that He might pray alone for His disciples placed in the Church as in a ship, and borne on in the faith of His Cross, as in wood, and in peril through this world's temptations as through the waves of the sea; His Name began to be honoured even in this world in which He was despised, accused, and slain; that He who in the dispensation of His suffering in the flesh, “had come into the depths of the sea, and the floods had overwhelmed Him,” might now through the glory of His Name tread upon the necks of the proud as on the foaming waters.
Just as we now see the Lord walking as it were upon the sea, under whose feet we behold the whole madness of this world subjected.
Source: Sermons on Selected Lessons of the New Testament (New Advent)