John 21:7 ESV
7 That disciple whom Jesus loved therefore said to Peter, It is the Lord! When Simon Peter heard that it was the Lord, he put on his outer garment, for he was stripped for work, and threw himself into the sea.
Peter was a different man than when Jesus first called him. He was still Simon Peter, with his enthusiasm and action, but made wiser in his time with Jesus and confrontations of his own failings. He was now stripped for the work Jesus had called him, for he had seen his own weakness with painful clarity. Pretensions were exposed and torn away, self serving ambitions had dissolved. He was now ready to answer "Yes" when Jesus would ask, "Do you love me?".
The Greek word εβαλεν, translated here as "threw", implies a disregard for the outcome. Peter once again leaves the boat and plunges into the sea. This time he swims to the Lord who waits on the shore, and he does not become afraid of the water.