Tony Bligh, from Dublin, caught a series of humps humps about 6ft apart moving through the water in unison on his mobile phone.
He posted the film on YouTube and it has already had over 22,000 views.
He said: “While visiting Loch Ness I noticed this weird formation on the loch near to Inverness end of the loch. Could it be the elusive Nessie?
“It was quite long. “The humps were consistently the same length apart. I don’t know what it was. It was very unusual.”
The film was taken last Wednesday at around noon from the A82.
Mr Bligh showed his film to staff in VisitScotland’s Inverness office, adding: “They were really excited by it. It is interesting everyone who has seen it on my telephone.”
However, he does admit there was a boot in the water about 400 yards from the series of four to five humps.
And Adrian Shine, of the Loch Ness Project in Drumnadrochit, claims it could be an optical illusion created by the wake of a boat.