[10] According to Adomnán, writing about a century after the events described, Irish monk Saint Columba was staying in the land of the Picts with his companions when he encountered local residents burying a man by the River Ness.

[15] In October 1871 (or 1872), D. Mackenzie of Balnain reportedly saw an object resembling a log or an upturned boat "wriggling and churning up the water," moving slowly at first before disappearing at a faster speed.

Both onlookers confessed that there was something uncanny about the whole thing, for they realised that here was no ordinary denizen of the depths, because, apart from its enormous size, the beast, in taking the final plunge, sent out waves that were big enough to have been caused by a passing steamer.

[27] Modern interest in the monster was sparked by a sighting on 22 July 1933, when George Spicer and his wife saw "a most extraordinary form of animal" cross the road in front of their car.

"[30] It had "an animal" in its mouth[28] and had a body that "was fairly big, with a high back, but if there were any feet they must have been of the web kind, and as for a tail I cannot say, as it moved so rapidly, and when we got to the spot it had probably disappeared into the loch.

However, in 1963, Maurice Burton came into "possession of two lantern slides, contact positives from th[e] original negative" and when projected onto a screen they revealed an "otter rolling at the surface in characteristic fashion.

[41] On April 20, 1934, multiple British newspapers reported Wilson's claim to have seen the monster while driving near Loch Ness the day before, but the stories do not mention the existence of a photograph.

[43] The following day, April 21, the Daily Mail announced it has purchased exclusive rights to a photo it attributed to "Mr. Robert Kenneth Wilson, M.A., M.B., Ch.B.Camb., F.R.C.S., of Queen Anne-street, W., who has been touring the Loch Ness countryside."

The photo's scale was controversial; it is often shown cropped (making the creature seem large and the ripples like waves), while the uncropped shot shows the other end of the loch and the monster in the centre.

In 1993, the makers of the Discovery Communications documentary Loch Ness Discovered analyzed the uncropped image and found a white object visible in every version of the photo (implying that it was on the negative).

[50] The creature was reportedly a toy submarine built by Christian Spurling, the son-in-law of actor, screenwriter, director, producer, and -- perhaps most saliently -- big-game hunter M. A. Wetherell.

Some believe it to be an earlier, cruder attempt at a hoax,[54] and others (including Roy Mackal and Maurice Burton) consider it a picture of a diving bird or otter that Wilson mistook for the monster.

[65][independent source needed] After the film, Dinsdale continued to pursue finding the Loch Ness Monster but while he claimed to have had additional sightings he was unable to produce more photographic evidence.

[68] Additionally, critics consider the dark shape noticed by the Discovery documentary analysis unlikely to be the shadow or a body underwater due to the low angle of view, and it is more likely to be reflections of the shore behind the object.

Edwards claims to have searched for the monster for 26 years, and reportedly spent 60 hours per week on the loch aboard his boat, Nessie Hunter IV, taking tourists for rides.

The device was fixed underwater at Temple Pier in Urquhart Bay and directed at the opposite shore, drawing an acoustic "net" across the loch through which no moving object could pass undetected.

[104] In 1972, a group of researchers from the Academy of Applied Science led by Robert H. Rines conducted a search for the monster involving sonar examination of the loch depths for unusual activity.

[108] During a meeting with Tony Harmsworth and Adrian Shine at the Loch Ness Centre & Exhibition, Rines admitted that the flipper photo may have been retouched by a magazine editor.

[109] British naturalist Peter Scott announced in 1975, on the basis of the photographs, that the creature's scientific name would be Nessiteras rhombopteryx (Greek for "Ness inhabitant with diamond-shaped fin").

[123] While investigating the depths of the loch, they found the resting place of a Nessie prop created for Billy Wilder's 1970 film The Private Life of Sherlock Holmes.

[125] An international team consisting of researchers from the universities of Otago, Copenhagen, Hull and the Highlands and Islands, did a DNA survey of the lake in June 2018, looking for unusual species.

The technology used included "sonar for mapping the loch bed; thermal imaging drones to scan the surface; and hydrophones (underwater microphones)" which did record some sounds, but were "probably ducks".

[139] According to biologist Bruce Wright, the Greenland shark could survive in fresh water (possibly using rivers and lakes to find food) and Loch Ness has an abundance of salmon and other fish.

[140][141] In July 2015 three news outlets reported that Steve Feltham, after a vigil at the loch that was recognized by the Guinness Book of Records, theorised that the monster is an unusually large specimen of Wels catfish (Silurus glanis), which may have been released during the late 19th century.

[66] In 1933, the Daily Mirror published a picture with the caption: "This queerly-shaped tree-trunk, washed ashore at Foyers [on Loch Ness] may, it is thought, be responsible for the reported appearance of a 'Monster'".

[147] In a 1982 series of articles for New Scientist, Maurice Burton proposed that sightings of Nessie and similar creatures may be fermenting Scots pine logs rising to the surface of the loch.

The seiche created in Loch Ness by the catastrophic 1755 Lisbon earthquake was reportedly "so violent as to threaten destruction to some houses built on the sides of it", while the 1761 aftershock caused two-foot (60 cm) waves.

[154] In 1979, W. H. Lehn showed that atmospheric refraction could distort the shape and size of objects and animals,[155] and later published a photograph of a mirage of a rock on Lake Winnipeg that resembled a head and neck.

It was later revealed that Flamingo Park education officer John Shields shaved the whiskers and otherwise disfigured a bull elephant seal that had died the week before and dumped it in Loch Ness to dupe his colleagues.

A popular explanation at the time, the following arguments have been made against it: In response to these criticisms, Tim Dinsdale, Peter Scott and Roy Mackal postulate a trapped marine creature that evolved from a plesiosaur directly or by convergent evolution.