New footage has emerged that its owner believes "could well be the Loch Ness Monster".
"Nessie" hunter Eoin O'Faodhagain, 59, regularly watches the famous Scottish body of water via a webcam from his home in Co Donegal in Ireland.
He believes he has spotted the creature once more in footage that shows something emerging from the water then sinking below the surface.
The footage was captured on 27 August during the biggest hunt for Nessie for more than 50 years, as hundreds of people swarmed the loch to try to spot the famous creature.
O'Faodhagain told the Daily Mirror he saw what "looked like the head and neck of something", which dipped below the surface, then a "long black object" with a "black, round, hump-like shape".
He added: "I thought it was very unusual – not just the fact that something rose up out of the water, but the manner in which it submerged, and the big black shape that appeared on the surface intrigued me. It could well be the Loch Ness Monster."
The footage was captured on a camera maintained by Visit Inverness Loch Ness.
The latest "sighting" followed the release of a new image following the biggest hunt for Nessie for more than 50 years.
Hundreds of Nessie hunters gathered at Loch Ness in Scotland last month to look for the famous monster.
Following the high-profile hunt, photographer Chie Kelly released a picture she took in 2018 that appears to show a creature in the water of the loch.
Read more on the hunt for the Loch Ness Monster:
The Loch Ness Monster: never before-seen picture emerges of Nessie (National World, 3 mins)
Loch Ness Monster sighting officially added to Nessie register (The National, 2 mins)
What's the story behind the Loch Ness Monster? (Herald Scotland, 3 mins)
However, paranormal investigator Hayley Stevens said she believes the creature in the photo is a fish.
She wrote on her blog: "I personally think it is most likely that they saw a large sturgeon in the loch. The photos were taken in August 2018 and sturgeon migrate into fresh water in late summer and early autumn to mate, before heading back out to coastal waters."
Sturgeons are among the largest fish and can grow to more than 5m in length.
The Nessie legend continues to capture the imagination, despite a number of false sightings and hoaxes down the years.
Read more: Nessie hunters hear ‘four distinctive noises’ in search for monster (PA Media, 2 mins)
About 200 volunteers were at Loch Ness month for the latest search, with hunters claiming to hear "four distinctive noises" in the water using an underwater microphone system.
Yahoo News UK examines the history of the Loch Ness Monster and the various theories about the famous beast:
When was the first sighting of the Loch Ness Monster?
The first reported "sighting" of the Loch Ness Monster was made by Irish monk Saint Columba in the year 565.
He reportedly caught a glimpse of the monster in the River Ness after he was told by locals that a man had been dragged underwater by it.
Read more: Biggest hunt for the Loch Ness Monster in 50 years gets under way (PA Media, 3 mins)
Columba sent one of his followers to swim across the water to find the monster. When it approached the follower, Columba made the sign of the cross and reportedly said: "Go no further. Do not touch the man. Go back at once."
The monster then stopped and fled, according to seventh century text, the Life of St Columba, written by Adomnán, an Irish abbot who lived in Scotland.
Is the Loch Ness monster real? What are the main theories?
Despite the original reported sighting by Saint Columba, and one or two further instances in the 1800s, interest in the creature didn't explode until 1933, when the first of a number of potential new sightings were recorded.
On 22 July of that year, George Spicer and his wife claimed to have spotted a creature cross the road in front of their car at the loch.
Read more: Couple 'want to believe’ they filmed Nessie before morning swim (Yorkshire Post, 2 mins)
Spicer said it was "the nearest approach to a dragon or prehistoric animal that I have ever seen in my life".
But in 2013, a study by Columbia University in New York debunked Spicer's claim, suggesting it was not true and inspired by a dinosaur in the movie King Kong, which had been released earlier in the year.
In November 1933, Hugh Gray took the first known photograph which claimed to depict the monster, although it was slightly blurred. He had taken his Labrador for a walk that day, and sceptics suggested the picture was of his pet fetching a stick from the loch, while others say it is an otter or a swan in the photo.
The following year, in 1934, saw the release of one of the most significant pieces of Nessie lore, the so-called "Surgeon's photograph".
Perhaps the most famous depiction of the monster, it was taken by gynaecologist Robert Kenneth Wilson and purportedly shows the head and neck of the beast coming out of the water of Loch Ness.
For about 60 years, it was seen as evidence of the monster's existence, but since the 1990s it is largely thought of as a hoax.
A 1999 book, Nessie - The Surgeon's Photograph Exposed, cited an obscure 1975 article from the Sunday Telegraph newspaper which revealed the creature in the photo was in fact a toy submarine purchased from Woolworth's, and that the head and neck were made from wood putty.
The official Loch Ness Monster sightings register continues to receive reports to this day, but scientists are adamant the creature is not real.
Read more: The hunt for Loch Ness Monster - what will emerge from the deep? (Herald Scotland, 3 mins)
They point to the fact that a large air-breathing mammal would have to surface from the waters frequently, which would have led to many more sightings.
Scuba divers have used sonar to search the lake on several occasions and found nothing, while a 2019 DNA study did not find evidence of a dinosaur or large reptile - believers often claim Nessie is a some kind of plesiosaur.
Read more: Loch Ness Monster ‘might be real’ say scientists after DNA tests (Yahoo News UK, 2 mins)
However, the water at Loch Ness is said to be only 10,000 years old, ruling out the presence of some kind of dinosaur, given they died out 65 million years ago.