As related in Matthew 14 where Simon joins Jesus in walking on the water, the Lord is manifesting His Divinity. In the OT it is GOD Who “walks upon the water.” We see also that it is God Who has power over the water, the place of chaos, the region where demonic powers dwell. This always harkens back to Genesis where God calls order - “Cosmos” – out of “chaos”. Water as chaos is the sense that we find in many of the prophets, in many of the psalms, going back to that primitive idea that this was the realm of dis-order. Now God in Genesis gives order to the water, and divides the water, bringing forth dry land, conquering watery chaos. Job, e.g., in Ch. 38 makes it a point that God puts His heel and walks upon the water, again an ancient sign of conquest – when the winner would come and place his heel on the head of the person vanquished, who humbly prostrated himself before his conquerer. Here it is the God-Man conquering watery chaos.
To add to this in these accounts (Jn. 6, e.g.) “Do not fear, it is I.” “Ego emi.” Also in His agony in the garden, “Ego emi”: “I am,” The Name of God. When Jesus walks on the water, doing what only YHWH does, He shows His creative power and His judgmental, governing, victorious power.
In Matthew’s presentation of the walking on the water we see an addition (because this is the ecclesial Gospel); Our Lord is asked by Peter in his usual blustery way: “Let me walk with you.” Peter is successfully walking on the water, but then he realizes his own frailty and takes his eyes off the Lord and begins to sink. Then Jesus takes him by the hand and keeps him from sinking in the water, and takes him to the boat, a symbol of the Church, the Apostolic boat, the barque of Peter where the Fishermen of the Church ply their trade – on which they are told by Christ, “henceforth you will be fishers of men.” But it is only Peter who walked on the water with Christ.
What has happened here? Peter is allowed to share, to participate in the prerogatives of Jesus. He is allowed to do what only God does. Peter is given certain powers of government, certain powers of judgment. There is a deep significance in this chapter, only two chapters before the great Petrine text of Matthew 16.