Peter saw a phenomenon, the interpretation of which needed to be achieved by answering the following questions: could Jesus have known that there were many fishes? Humanly - no!
But even had He known it by divine inspiration, it is not a knowledge of a static thing, but of a caravan of fishes who change their position all the time in a matter of seconds; so, Peter was initially hesitant and started to procrastinate by complaining that he had tried all night; now, had Peter not procrastinated he would have caught those fishes, but even as he procrastinated, he achieved the same. Now this is possible only if Jesus Himself made fishes not to swim anywhere, but to swim into Peter’s nets the moment he would put them into the water. And He did that authoritatively and confidently, without prayers.
Now, could angels force fishes to do so? No. Prophets and saints? - No. Is it a prerogative of only God? Yes. Only and exclusively. Thus it obtains that Jesus holds the same sovereign authority over the created nature as only God holds; therefore, in virtue of holding such a sovereign authority, so as to govern powers of nature at will, Jesus is God.
Peter being awed for that matter, asked Him to leave him, for he felt himself utterly unworthy.