John 21:7; John 21:20; John 21:24
Then the disciple whom Jesus loved said to Peter, "It is the Lord!" When Simon Peter heard that it was the Lord, he put on his tunic (for he had stripped for work), jumped into the water, and swam ashore.
Peter turned around and saw the disciple Jesus loved following them -- the one who had leaned over to Jesus during supper and asked, "Lord, who among us will betray you?"
This is that disciple who saw these events and recorded them here. And we all know that his account of these things is accurate.