Let's admit it: today's Gospel reading tells a freaky story. We're used to it, of course; so used to it that we use the term "walking on water" to mean "Godlike."* But even by the standards of the Incarnation, this episode is on the extreme side.
And how, exactly, did Peter's mind work. "Do not be afraid? Got it. Let's see, there aren't any lions here to punch, no scorpions to juggle, so... hey, why don't I jump out of the boat and walk around? That would be pretty scary to do, ordinarily."
Still, there's a lot to chew on once you get past the over-the-top action. The inability of the disciples to make headway without Jesus being present; the willingness of Peter to follow His Lord in action; his too-human failing.
What strikes me this time around, though, is how quickly Jesus acts:
At once Jesus spoke to them... He said, "Come." ... Immediately Jesus stretched out his hand...
When the disciples are frightened, Jesus reassures them "at once." When Peter asks for an invitation to demonstrate his faith, Jesus gives him one in a single word. And when Peter gets in over his head, Jesus rescues him "immediately."
When Jesus says, "Be not afraid," He seems to mean it. That is, He doesn't mean, "Work on overcoming your fears, and when you've done that, then don't return to being afraid." He means, I think, "Stop being afraid this instant. Don't you know who I AM? Don't you know that I AM with you in this instant right now?"
We don't need to be afraid of God's dominion over creation, the way we might be afraid of a ghost's indifference to physics, because God is good. And we need to not be afraid because fear keeps us where we are -- in a boat fighting the wind, say, instead of stepping forth in faith to make the Gospel known.
*Actually, per Mt 14:33, walking on water is Son-of-God-like. The first reading tells us that what's Godlike is a tiny whispering sound, but "tiny whispering sound" hasn't really caught on as an idiom.