In 1969, the Billy Wilder movie The Private Life of Sherlock Holmes was filmed on location in Urquhart Bay. The plot involves secret submarine tests in Loch Ness, with the test sub disguised as a lake monster - Sherlock's brother Mycroft (played by Sir Christopher Lee) is wrapped up in all of this. It seems that Billy Wilder didn't like the double hump of the Nessie model and had it removed - unfortunately, the design of the humps were part of what allowed for buoyancy for the 40 foot beastie. So, as it was towed out into the bay, it sank beneath the waves and was abandoned- the scenes involving the movie monster used a rebuilt head and neck at a London water tank.
The AAS continued to believe that the underwater photo they captured in 1975 showed a genuine living creature, despite the insistence by the press and skeptics that they had simply found the movie prop. Also, the area where the model was recently found has been a hotspot for Nessie sightings in recent years. Maybe the sunken model is something of a roadside attraction, or a sacred idol to the monsters of the Loch? Perhaps Nessie simply wants a selfie with her Hollywood double...
Joseph W. Zarzynski's 1986 book Monster Wrecks of Loch Ness and Lake Champlain covers this and other stories of sunken boats and crashed planes in both lakes, and is certainly worth reading for the lake monster fanatic. For more information on the underwater robot mentioned at the top, look here.
That wraps up Nessie-a-Day #2!