The legend of Nessie has long captured people's imagination. Photo:
Hundreds of people are set to join what has been described as the biggest search for the Loch Ness Monster in more than 50 years.
Two hundred volunteers are to help record natural - and any unusual - sights on Loch Ness from vantage points on land.
Almost 300 have signed up to monitor a live stream from the search, which is taking place on Saturday and Sunday local time.
It is 90 years since the modern myth of Nessie began.
In April 1933, hotel manageress Aldie Mackay said she had seen a whale-like creature in the loch.
The Inverness Courier newspaper reported the sighting and the editor at the time, Evan Barron, suggested the creature be described as a "monster".
Since then the mystery of Nessie has inspired books, TV shows and films, as well as sustaining a major tourism industry.
This weekend's search has been organised by the Loch Ness Centre in Drumnadrochit and a volunteer research team called Loch Ness Exploration.
Drones fitted with infrared cameras are to be flown over the loch, and a hydrophone is to be used to detect unusual underwater sounds.
Alan McKenna, of Loch Ness Exploration, told BBC Radio's Good Morning Scotland programme: "We are looking for breaks in the surface and asking volunteers to record all manner of natural behaviour on the loch."
He said the loch could play tricks on people's eyes and mind.
"Not every ripple or wave is a beastie. Some of those can be explained, but there are handful that cannot," he added.
Loch Ness Centre general manager Paul Nixon added: "The interest in our weekend of activities has been fantastic, and to see how people from all around the world are still fascinated by the story of the loch and Nessie.
"We want anyone in the world to be able to help, which is why we are looking for budding monster hunters from anywhere to log in to the live stream of the loch over the weekend and see if they spot anything mysterious.
"We can't wait to see what we find."
Organisers said the effort would be the biggest search for the monster since the Loch Ness Investigation Bureau carried out a study in 1972.
The bureau was set up in the 1960s to find proof of a large beast in the waters.
It was wound up in 1977 after it was unsuccessful in uncovering any significant evidence for or against the existence of a monster.
The legend of Nessie dates back to the Middle Ages when Irish monk St Columba is said to have encountered a beast in the Ness, a river that flows from Loch Ness.
Previous attempts to find the monster included 1987's Operation Deepscan, when 24 boats equipped with echo sounders swept the entire length of the loch.
On three occasions something was detected that could not be immediately explained. Large debris was one of the explanations offered for the "contacts".
In 2019, scientists said the creatures behind repeated sightings of the fabled Loch Ness Monster may be giant eels.
Researchers from New Zealand tried to catalogue all living species in the loch by extracting DNA from water samples.
Following analysis, the scientists ruled out the presence of large animals which were said to be behind reports of a monster.
No evidence of a prehistoric marine reptile called a plesiosaur or a large fish such as a sturgeon were found.
Loch Ness is Scotland's largest freshwater loch by volume.
It can hold more water - 7452 million cubic metres - than all English and Welsh lakes together.
- This story was first published by the BBC