"Nessie" is an alleged creature living in Loch Ness, a long, deep lake near Inverness, Scotland. Many sightings of the "monster" have been recorded, going back at least as far as St. Columba, the Irish monk who converted most of Scotland to Christianity in the 6th century. Columba apparently converted Nessie, too; for it is said that until he went out on the waters and soothed the beast, she had been a murderess.
The modern legend of Nessie begins in 1934 with Dr. Robert Kenneth Wilson, a London physician, who allegedly photographed a plesiosaur-like beast with a long neck emerging out of the murky waters. That photo created quite a fuss. Before the photo, Loch Ness was the stuff of legend and myth. The locals knew the ancient history of the sea serpent. But people came to the lake more to relax than to go on expeditions looking for mythical beasts. After the photo, the scientific experts were called in. First, they examined the photo itself. Could be a plesiosaur. Yes, but it could be a tree trunk, too. Or an otter. Later, there would be explorations by a submarine with high tech sensing devices.