Photo via Modern Mechanix
In 1934, Dr. Robert Wilson (a practicing gynecologist) claimed to have stumbled upon a monster discovery. He photographed something that honestly looked like a Plesiosaur. He sent his images into the local papers and it was intitially published in the British Newspaper Daily Mail. For 41 years it was regarded as the truth and evidence of a mythical creature. But many years later on December 7, 1975, The Sunday Telegraph (another UK Newspaper) revealed the image to be an outright phony. By 1993, The Discovery Channel featured a documentary – Loch Ness Discovered – and had done some careful analysis on an uncropped version of the fabled photograph; they discovered that there was an irregularity in the way.
The photo is talked about in the Museum of Hoaxes. However, people claim to have seen Nessy in other places as well. And submarine expeditions have been taken to try to find the creature–but nothing has been fruitful.