You may have wondered what the very first sighting of Nessie was. It's a good question. Wasn't it in 1934 when the famous Surgeon's photo was taken? No. Actually, the very first reported sighting was in 565 A.D.
Saint Columba was born c. 521 in Donegal of the royal Ui Neill clan, and trained as a monk under St. Finnian. He later founded the monasteries of Derry, Durrow, and Kells, before leaving Ireland at the age of forty-two with twelve companions. He then founded the world-famous monastery on the island of Iona, off southwest Scotland, before continuing on his way to the Highlands.
After arriving at Loch Ness in 565 A.D., the saint began preaching among the pagan Picts. The holy man even attended the funeral ceremony of one unfortunate fellow who had been killed by a water beast. One day, the saint desired to cross the loch near the River Ness, but the only available boat had drifted into the water. A local man by the name of Lugne Mocumin plunged into the water and swam out to retrieve the drifting vessel. The water suddenly started to churn, when, without warning, an enormous creature broke the surface near the swimming man. The crowd on the banks of the loch fell back in horror at the sight of the beast as it raced toward Mocumin. Ordering his followers to be silent, Saint Columba at once raised his hand, and making the sign of the cross in the air, loudly commanded the monster to depart: "Go no further, and touch not the man!"
The monster retreated more quickly than it had advanced. Then, the horrified Mocumin, reaching the boat, rowed it safely back to the shore.
Needless to say, the local populace embraced Christianity.
This is the earliest reported encounter with the Loch Ness Monster. This event was actually recorded 100 years later by the biographer Adamnan, who was also connected to Saint Columba's monastery on Iona.
Sources: Missionaries and Monsters Gibbons, William J. Coachwhip Publications 2006 p. 11 and Claws, Jaws, and Dinosaurs Gibbons, William J. and Hovind, Dr. Kent CSE Publications 1999 p. 9