Its serpentine neck and partially submerged humps make for one the world's most recognisable images, and have inspired numerous hoaxes, films and advertisements.
Now the Loch Ness monster is the object of a bitter feud over attempts by businessmen based on the shores of its watery domain to transform it into a multi-million pound marketing concept.
On one side is a group of Highland entrepreneurs itching to exploit the global pull of the "Nessie brand". On the other is a collection of amateur enthusiasts and local small businesses who fear that opening up the loch to greater commercialism will cheapen the legend and suck the lifeblood from their village of Drumnadrochit.
The tensions are being played out between three rival internet sites linked to separate 24-hour webcams located at vantage points around and within the loch.
Lochness Live! – catchphrase, "Loch Ness: More than a Monster" – features plugs for local hotels and cruise companies alongside invitations to "spot Nessie live on camera". It is the work of Willie Cameron, director of the newly launched Loch Ness Marketing and the architect of a decision by Drumnadrochit Chamber of Commerce to re-name itself Visitlochness Ltd.
A second, more scientific, site is overseen by Adrian Shine, a naturalist and confessed Nessie "non-believer'" who runs Loch Ness 2000, a hi-tech visitor centre situated next-door to Mr Cameron's business HQ, the Drumnadrochit Hotel.
The third is the work of Mikko Takala, a computer programmer and pioneer of webcams at Loch Ness, who claims his idea has been "hijacked" by interlopers.
Mr Takala, an opponent of what he calls "the Drumnadrochit mafia", said: "The webcams started out as a bit of fun, a way of enabling people around the world to look for the Loch Ness monster. Now the suits have hijacked it, and just tried to make money out of it. Their websites are like glorified telephone directories."
Though he stopped short of suggesting his website had ever been deliberately sabotaged, Mr Takala said there had been inexplicable "periods where it's been off line".
For the past few months, Mr Takala has used his site, Nessie on the Net, to lambast a recently completed £5m re-development of Urquhart Castle, the dramatic medieval ruin overlooking the loch, as well as those, like Mr Cameron, who supported it.
Mr Cameron and his business associate Fraser Campbell, who runs the Drumna- drochit Hotel, are directors of the Loch Ness Coffee Company, which runs the tea room at the new centre. Their latest venture has caused ripples in the village, where other café owners say they have lost a third of their trade since the castle reopened last October.
Among the losers is Donald Skinner, owner of the more traditional of the village's two Nessie attractions, The Original Loch Ness Visitor Centre – motto, "we believe" – and a pint-sized Disney castle called The Braveheart Centre.
Mr Skinner, who also owns the neighbouring Drumnadrochit Lodge Hotel, criticised the "two-way traffic" which sees coachloads of tourists bypassing the village en route from Inverness to Urquhart via Loch Ness 2000. "Every pound spent there is a pound less spent in the village."
Mr Cameron remains bullish. Describing the monster as "living X-Files" and "a brand that could be bigger than Coke", he said: "My whole aim is to bring business into Drum."
As for the Net rivalries, he said: "Yes, we're using our webcam to market Loch Ness, but there's nothing wrong with that. And Mikko didn't invent webcams: the idea for ours came from a guy in the village supermarket."
Gary Campbell, of the Loch Ness Monster Fan Club, said: "There's a scene in the film Loch Ness where two men are fighting in the water and yelling, 'it's my monster, it's my monster'. That sums it up. Everyone wants to own the Loch Ness monster."
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