John 21:7 (NASB)
It is the Lord!
If the Lord were to walk among us today, would we recognize Him? The Apostles certainly couldn't recognize Him immediately. But when He spoke and told them to cast their net, there was something familiar about the voice. They had heard that voice before. Then there was the miraculous catch of fish followed by a breakfast when that stranger from Galilee broke bread and gave thanks. They've seen that before too. They remembered how they traveled and ate with that itinerant preacher who performed miracles. These simple acts of fellowship and His Presence helped them recognize Him.
If we spend time with Him, we can recognize Him too.