London The Loch Ness monster is a Loch Ness myth.
That's the conclusion of the British Broadcasting Corp., which says a research team that trawled the lake came up with no signs of the famous Nessie.
The team used 600 separate sonar beams and satellite navigation technology to sweep the entire loch, but found no trace of a monster or any other large creature, the BBC reported this week.
Over the centuries, reported sightings of a big beast in the gray waters of the lake have led many people to believe it holds some huge creature although a series of searches has found no evidence of one.
Some enthusiasts have even speculated Nessie might be a descendant of a plesiosaur, a marine reptile that died out with the dinosaurs.
The BBC researchers said they looked at the habits of modern marine reptiles, such as crocodiles and leatherback turtles, to try to work out how a plesiosaur might behave.
"We went from shoreline to shoreline, top to bottom on this one. We have covered everything in this loch and we saw no signs of any large living animal in the loch," said Ian Florence, one of the specialists who carried out the survey for the BBC.
The BBC team said the only explanation for the persistence of the monster myth -- and its periodic "sightings" -- is that people see what they want to see.
To test this, the researchers hid a fence post beneath the surface of the loch and raised it in view of a bus full of tourists.
Interviewed afterward, most said they had observed a square object, but when asked to sketch what they saw, several drew monster-shaped heads, the BBC said in a program broadcast Sunday.
There have been reports of sightings of a "monster" in the loch since the time of St. Columba in the 6th century.
Many who have reported sightings have described a beast similar to a plesiosaur, but experts say the most recent fossil of one dates from 65 million years ago. Loch Ness is only 10,000 years old.