Why would he do this? In the Gospel of Mark we see that Jesus does a lot of miracles: he has just fed 5000 people with someone’s packed lunch. But what is the point of walking on the water? Is it just a cool trick? I must admit I would be rather impressed; it would certainly get your attention right?
The disciples are afraid when they see Jesus walking on the water and he says to them “take heart, it is I, do not be afraid.” The phrase “it is I” in the Greek could be understood as “I am” which echoes the language of God to Moses when he reveals himself in the burning bush (Exodus 3).
So, in sum:
This passage is more than a cool trick. Jesus walks on the water, “passing by” and announcing, “I am”. The message is clear: Jesus is divine!