Amateur photographer David Elder claims a “solid black object” gliding beneath the lake’s surface caused the sudden ripple.
David, 50, was focusing in a swan at Fort Augustus on the south-west end when he spotted the “creature”.
David, of East Kilbride, said: “Out of the corner of my right eye I caught site of a black area of water about 15ft 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.
"It is something I just can't explain."
The Loch Ness Monster has been a subject of mass debate since it first came to the world's attention 80 years ago.
His shot may not have the iconic status of Colonel Robert Kenneth Wilson’s 1934 shot of Nessie, which was later explained as a hoax.
But it is sure to cause a tide of speculation among monster hunters.
Scientists have widely written off the idea as a modern-day myth yet it has remained a contested phenomenon.
Perhaps the most famous picture of Nessie (right) was taken in 1934 by Robert Kenneth Wilson, a London gynaecologist.
The picture showed what looked like a long neck and head rising from the water.
However, it turned out to be a toy submarine bought from Woolworths in an hoax set up by Marmaduke Wetherell, who had been ridiculed by the national press over his hapless search for the beast.
Source: Mirror UK