‘But he says to them, “It is I. Don't be afraid”. They were therefore willing to receive him into the boat, and immediately the boat was at the land where they were going.'
To their relief and surprise the figure turned out to be Jesus, and, when He made Himself known to them they were highly relieved, and gladly brought Him into the boat. And it was not long after this that they made land safely.
‘It is I' is literally ‘I am'. John may be intending to draw out that Jesus is the ‘I am', as he certainly does later (John 8:58).
‘Immediately the boat was at the land where they were heading.' The idea is probably not of a miraculous moving of the boat, but of John's memory of the night. He remembers their overwhelming joy and relief so that in what seemed no time at all they arrived at land. This was because the wind dropped, as the other Gospels tell us, and Jesus was with them in the boat, making the remainder of the journey seem short and easy (Mark 6:51). ‘Immediately' is a hurry word. It indicates a short period of time.
Some scholars have tried because of this to suggest that what they actually saw was Jesus walking on the seashore, and wished to, but could not, take Him into the boat, because they were already at the shore. In John such a translation is possible, but it is not the natural translation and would require another boat to take Jesus across and a bunch of hardy sailors who never afterwards told the truth, for the other Gospels are in no doubt on the matter.
But we must not forget in this regard that some of them were experienced sailors and knew the Sea of Galilee well, and seeing Jesus on the shore would not have frightened them, nor would it have misled them. They were used to discerning the shoreline and seeing people on it. Besides, the distance travelled indicates that they were well out at sea. There can really be no doubt that the author sees the walking on the water as another sign. The other Gospels make the situation quite plain. Indeed the crowds act as indirect witnesses to the reality (John 6:22-25).
The importance of the incident is found in the Old Testament where it is clear that the One Who can walk on water is the omnipotent God - ‘your way was through the sea, your path through the great waters' (Psalms 77:19). This was thus a direct claim to deity. To Israel the sea had always appeared as an enemy and a symbol of tumult. In their eyes there was only One Who could control it and that was their God. It also, of course, taught the disciples a great lesson about the powers of Jesus. In future when they faced great difficulties they could look back on this incident and be aware that whatever their circumstances He was with them and could meet all their needs.