Is it the Loch Ness Monster? Or is it, er, a big wave?
Amateur photographer David Elder is convinced the image shows a solid black object moving swiftly up the famed Loch - where the elusive Nessie is said to dwell.
The 50-year-old said: '"We were at the pier head at Fort Augustus and I was taking a picture of a swan at the time.
"Out of the corner of my right eye I caught site of a black area of water about 15 feet long which developed into a kind of bow wave.
"I'm convinced this was caused by a solid black object under the water. The water was very still at the time and there were no ripples coming off the wave and no other activity on the water. Water was definitely going over something sold and making the wave.
"It looks like the sort of wave perhaps created by a windsurfing board but there was nobody on the Loch at the time, no boats, nothing.
"The disturbance in the water began moving up the Loch sideways. It is something I just can't explain."
The murky waters of the Loch are said to have been haunted by the serpentine Scottish beast since 1933.
Believed by many to be the last of a line of long-surviving plesiosaurs (a Jurassic marine reptile) legend has it that the creature appears along with earth tremors and swirling bubbles.
However, in July an Italian geologist declared a fault line which runs for 62 miles beneath the Scottish Highlands could be responsible for the sightings.
Luigi Piccardi told La Repubblica: ""There are various effects on the surface of the water that can be related to the activity of the fault.
"We know that this was a period [1920-1930] with increased activity of the fault. In reality, people have seen the effects of the earthquakes on the water."
However he did not offer an explanation for pictures of the monster. Nessie first hit headlines in 1934 when the Daily Mail published the above picture.
The photo was later revealed to have been staged, but there has been no shortage of images since.
In 2012 A sailor who spent 26 years searching for the Loch Ness Monster took what he believes is the best ever picture taken of the elusive beast.
This argument was used to support the existence of Nessie by Gary Campbell, president of the Loch Ness Monster Fan Club in Inverness, Scotland. "Most of the sightings involve foreign objects coming out of the water. There's two most common -- one's a hump, and the other is a head and neck," Campbell told ABC News.
"At the end of the day, there are still sightings that are inexplicable. There's something physical in there."