It is connected at the southern end by the River Oich and a section of the Caledonian Canal to Loch Oich. At the northern end there is the Bona Narrows which opens out into Loch Dochfour, which feeds the River Ness and a further section of canal to Inverness. It is one of a series of interconnected, murky bodies of water in Scotland; its water visibility is exceptionally low due to a high peat content in the surrounding soil.

Loch Ness is the second largest Scottish loch by surface area at 56.4 km2 (21.8 sq mi) after Loch Lomond, but due to its great depth it is the largest by volume. Its deepest point is 230 m (754 ft), deeper than the height of London's BT Tower at 189 m (620 ft) and deeper than any other loch with the exception of Loch Morar. It contains more fresh water than all lakes in England and Wales combined, and is the largest body of water on the Great Glen Fault, which runs from Inverness in the north to Fort William in the south.

The term "monster" was reportedly coined on 2 May 1933 by Alex Campbell, the water bailiff for Loch Ness and a part-time journalist, in a report in the Inverness Courier. On 4 August 1933, the Courier published as a full news item the claim of a London man, George Spicer, that a few weeks earlier while motoring around the Loch, he and his wife had seen "the nearest approach to a dragon or pre-historic animal that I have ever seen in my life", trundling across the road toward the Loch carrying "an animal" in its mouth. Other letters began appearing in the Courier, often anonymously, with claims of land or water sightings, either on the writer's part or on the parts of family, acquaintances or stories they remembered being told. These stories soon reached the national (and later the international) press, which talked of a "monster fish", "sea serpent", or "dragon", eventually settling on "Loch Ness Monster". On 6 December 1933 the first purported photograph of the monster, taken by Hugh Gray, was published, and shortly after the creature received official notice when the Secretary of State for Scotland ordered the police to prevent any attacks on it. In 1934, interest was further sparked by what is known as The Surgeon's Photograph. In the same year R. T. Gould published a book, the first of many which describe the author's personal investigation and collected record of additional reports pre-dating the summer of 1933. Other authors made claims that sightings of the monster went as far back as the 6th century (see below).

The earliest report of a monster associated with the vicinity of Loch Ness appears in the Life of St. Columba by Adomnán, written sometime during the 7th century. According to Adomnán, writing about a century after the events he described, the Irish monk Saint Columba was staying in the land of the Picts with his companions when he came across the locals burying a man by the River Ness. They explained that the man had been swimming the river when he was attacked by a "water beast" that had mauled him and dragged him under. They tried to rescue him in a boat, but were able only to drag up his corpse. Hearing this, Columba stunned the Picts by sending his follower Luigne moccu Min to swim across the river. The beast came after him, but Columba made the sign of the cross and commanded: "Go no further. Do not touch the man. Go back at once." The beast immediately halted as if it had been "pulled back with ropes" and fled in terror, and both Columba's men and the pagan Picts praised God for the miracle. Believers in the Loch Ness Monster often point to this story, which notably takes place on the River Ness rather than the loch itself, as evidence for the creature's existence as early as the 6th century. However, sceptics question the narrative's reliability, noting that water-beast stories were extremely common in medieval saints' Lives; as such, Adomnán's tale is likely a recycling of a common motif attached to a local landmark.

According to the skeptics, Adomnán's story may be independent of the modern Loch Ness Monster legend entirely, only becoming attached to it in retrospect by believers seeking to bolster their claims. Additionally, in an article for Cryptozoology, A. C. Thomas notes that even if there were some truth to the story, it could be explained rationally as an encounter with a walrus or similar creature that had gotten up the river.

Binns acknowledges that this account is the most serious of various alleged early sighting of the monster, but argues that all other claims of monster sightings prior to 1933 are highly dubious and do not prove that there was a tradition of the monster before this date.

Spicers (1933)
Modern interest in the monster was sparked by the 22 July 1933 sighting, when George Spicer and his wife saw 'a most extraordinary form of animal' cross the road in front of their car.They described the creature as having a large body (about 4 feet (1 m) high and 25 feet (8 m) long), and long, narrow neck, slightly thicker than an elephant's trunk and as long as the ten- to twelve-feet (3.0–3.7 m) width of the road; the neck had a number of undulations in it. They saw no limbs, possibly because of a dip in the road obscuring the animal's lower portion. It lurched across the road towards the loch 20 yards (20 m) away, leaving only a trail of broken undergrowth in its wake.

In August 1933 a motorcyclist named Arthur Grant claimed to have nearly hit the creature while approaching Abriachan on the north-eastern shore, at about 1 am on a moonlit night. Grant claimed that he saw a small head attached to a long neck, and that the creature saw him and crossed the road back into the loch. Grant said he dismounted and followed it to the loch, but only saw ripples. However some believe this story was intended as a humorous explanation of a motorcycle accident.

In another 1933 sighting, a young maidservant named Margaret Munro supposedly observed the creature for about 20 minutes. She claimed it was about 6:30 am on 5 June, when she spotted it on shore from about 200 yards (180 m). She described it as having elephant-like skin, a long neck, a small head and two short forelegs or flippers. The sighting apparently ended when the creature re-entered the water.

Sporadic land sightings continued until 1963, when a poor-quality film of the creature was made from a distance of several miles.

C.B. Farrel (1943)
In May 1943, C. B. Farrel of the Royal Observer Corps was supposedly distracted from his duties by a Nessie sighting. He claimed to have been about 250 yards (230 m) away from a large-eyed, 'finned' creature, which had a twenty- to thirty-foot (6–9 m) long body, and a neck that protruded about 4-5 feet (1.2-1.5 m) out of the water.

Sonar contact (1954)
In December 1954 a strange sonar contact was made by the fishing boat Rival III. The vessel's crew observed sonar readings of a large object keeping pace with the boat at a depth of 480 feet (146 m). It was detected travelling for half a mile (800 m) in this manner, before contact was lost, but then found again later. Many sonar attempts had been made previously, but most were either inconclusive or negative.

Photographs and films

The 'Surgeon's Photograph' (1934)

The Surgeon's PhotographOne of the most iconic images of Nessie is known as the 'Surgeon's Photograph', which many formerly considered to be good evidence of the monster. Its importance lies in the fact that it was the only photographic evidence of a “head and neck” – all the others are humps or disturbances. The image was revealed as a hoax in 1994.

Supposedly taken by Robert Kenneth Wilson, a London gynaecologist, it was published in the Daily Mail on 21 April 1934. Wilson's refusal to have his name associated with the photograph led to its being called "Surgeon's Photograph". The ripples on the photo fit the size and circular pattern of small ripples as opposed to large waves when photographed up close. Analyses of the original uncropped image have fostered further doubt. A year before the hoax was revealed, the makers of Discovery Communications's documentary Loch Ness Discovered analysed the uncropped image and found a white object was visible in every version of the photo, implying it was on the negative. "It seems to be the source of ripples in the water, almost as if the object was towed by something", the narrator said. "But science cannot rule out it was just a blemish on the negative", he continued. Additionally, analysis of the full photograph revealed the object to be quite small, only about 60 to 90 centimetres (two to three ft) long.

In 1979 it was claimed to be a picture of an elephant (see below). Other sceptics in the 1980s argued the photo was that of an otter or a diving bird, but after Christian Spurling's confession most agree it was what Spurling claimed - a toy submarine with a sculpted head attached. The details of how it was done have been given in a book. Essentially, it was a toy submarine with a head and neck made of plastic wood, built by Christian Spurling, the son-in-law of Marmaduke Wetherell, a big game hunter who had been publicly ridiculed in the Daily Mail, the newspaper that employed him. Spurling claimed that to get revenge, Marmaduke Wetherell committed the hoax, with the help of Chris Spurling (a sculpture specialist), his son Ian Marmaduke, who bought the material for the fake Nessie, and Maurice Chambers (an insurance agent), who would call to ask surgeon Robert Kenneth Wilson to offer the pictures to the Daily Mail. The hoax story is disputed by Henry Bauer, who claims this debunking is evidence of bias, and asks why the perpetrators did not reveal their plot earlier to embarrass the newspaper. He also claimed that plastic wood did not exist in 1934, although it was a popular DIY and modelling material in the early 1930s.

Alastair Boyd, one of the researchers who uncovered the hoax, argues the Loch Ness Monster is real, and that the hoaxed Surgeon's Photo is not cause enough to dismiss eyewitness reports and other evidence.

Taylor film (1938)
In 1938, G.E. Taylor, a South African tourist, filmed something in the loch for three minutes on 16 mm colour film, which is now in the possession of Maurice Burton. However, Burton has refused to show the film to Loch Ness investigators (such as Peter Costello or the Loch Ness Investigation Bureau). A single frame was published in his book The Elusive Monster; before he retired. Roy P. Mackal, a biologist and cryptozoologist, declared the frame to be "positive evidence". Later, it was shown also to the National Institute of Oceanography, now known as the Southampton Oceanographic Centre. It was agreed by the experts that the film clearly showed an ordinary inanimate object floating in the Loch.[citation needed]

Dinsdale film (1960)
In 1960, aeronautical engineer Tim Dinsdale filmed a hump crossing the water in a powerful wake unlike that of a boat. JARIC declared that the object was "probably animate". Others were sceptical, saying that the "hump" cannot be ruled out as being a boat, and claimed that when the contrast is increased a man can be clearly seen in a boat.

In 1993 Discovery Communications made a documentary called Loch Ness Discovered that featured a digital enhancement of the Dinsdale film. A computer expert who enhanced the film noticed a shadow in the negative which was not very obvious in the positive. By enhancing and overlaying frames, he found what appeared to be the rear body, the rear flippers, and 1-2 additional humps of a plesiosaur-like body. He said that: "Before I saw the film, I thought the Loch Ness Monster was a load of rubbish. Having done the enhancement, I'm not so sure". Some have countered this finding by saying that the angle of the film from the horizontal along with sun's angle on that day made shadows underwater unlikely. Believers (and some non-believers) claim the shape could have been undisturbed water that was only coincidentally shaped like a plesiosaur's rear end. But the same source also says that there might be a smaller object (hump or head) in front of the hump causing this. Nonetheless, the enhancement did show a smaller second hump and possibly a third hump.

Holmes video (2007)
On 26 May 2007, Gordon Holmes, a 55-year-old lab technician, captured video of what he said was "this jet black thing, about 45 feet (14 m) long, moving fairly fast in the water." Adrian Shine, a marine biologist at the Loch Ness 2000 centre in Drumnadrochit, has watched the video and plans to analyze it. Shine also described the footage as among "the best footage [he has] ever seen." BBC Scotland broadcast the video on 29 May 2007. STV News' North Tonight aired the footage on 28 May 2007 and interviewed Holmes. In this feature, Adrian Shine of the Loch Ness Centre was also interviewed and suggested that the footage in fact showed an otter, seal or water bird.

Holmes's credibility has been doubted by an article on the Cryptomundo website, which states that he has a history of reporting sightings of cryptozoological creatures, and sells a self-published book and DVD claiming evidence for fairies. His video also has no other objects by which to discern size. The Monster Quest team investigated this video as well in their TV episode "Death of Loch Ness", where they examine evidence that Nessie has died, as well as other photos.

Loch Ness Phenomena Investigation Bureau (1962-1972)
The Loch Ness Phenomena Investigation Bureau (LNPIB) was a UK-based society formed in 1962 "to study Loch Ness to identify the creature known as the Loch Ness Monster or determine the causes of reports of it."[citation needed] It later shortened the name to Loch Ness Investigation Bureau (LNIB). It closed in 1972. The society had an annual subscription which covered administration. Its main activity was for groups of self-funded volunteers to watch the loch from various vantage points, equipped with cine cameras with telescopic lenses. Its founders included MP David James and naturalist Peter Scott. From 1965 to 1972 it had a caravan camp and main watching platform at Achnahannet, and sent observers to other locations up and down the loch. According to the 1969 Annual Report of the Bureau, it had 1,030 members, of whom 588 were from the UK. Its directors were listed as Norman Collins (Chairman), Lord Craigmyle, Prof. Roy P. Mackal, R. S. R. Fitter, David James, MP, and Peter Scott.

The LNPIB sonar study (1967-1968)
Professor DG Tucker, chairman of the Department of Electronic and Electrical Engineering at the University of Birmingham, England, volunteered his services as a sonar developer and expert at Loch Ness in 1968. The gesture was part of a larger effort helmed by the LNPIB from 1967-1968 and involved collaboration between volunteers and professionals in various fields. Tucker had chosen Loch Ness as the test site for a prototype sonar transducer with a maximum range of 800 metres (2600 ft). The device was fixed underwater at Temple Pier in Urquhart Bay and directed towards the opposite shore, effectively drawing an acoustic 'net' across the width of Ness through which no moving object could pass undetected. During the two-week trial in August, multiple animate targets six metres (20 ft) in length were identified ascending from and diving to the loch bottom. Analysis of diving profiles ruled out air-breathers because the targets never surfaced or moved shallower than midwater. A brief press release by LNPIB and associates touched on the sonar data and drew to a close the 1968 effort:

“ The answer to the question of whether or not unusual phenomena exist in Loch Ness, Scotland, and if so, what their nature might be, was advanced a step forward during 1968, as a result of sonar experiments conducted by a team of scientists under the direction of D. Gordon Tucker... Professor Tucker reported that his fixed beam sonar made contact with large moving objects sometimes reaching speeds of at least 10 knots (19 km/h). He concluded that the objects are clearly animals and ruled out the possibility that they could be ordinary fish. He stated: "The high rate of ascent and descent makes it seem very unlikely that they could be fish, and fishery biologists we have consulted cannot suggest what fish they might be. It is a temptation to suppose they might be the fabulous Loch Ness monsters, now observed for the first time in their underwater activities!" ”

Andrew Carroll's sonar study (1969)
In 1969 Andrew Carroll, field researcher for the New York Aquarium in New York City, proposed a mobile sonar scan operation at Loch Ness. The project was funded by the Griffis foundation (named for Nixon Griffis, then a director of the aquarium). This was the tail-end (and most successful portion) of the LNPIB's 1969 effort involving submersibles with biopsy harpoons. The trawling scan, in Carroll's research launch Rangitea, took place in October. One sweep of the loch made contact with a strong, animate echo for nearly three minutes just north of Foyers. The identity of the contact remains a mystery. Later analysis determined that the intensity of the returning echo was twice as great as that expected from a 10-foot (3 m) pilot whale. On returning to the University of Chicago, biologist Roy Mackal and colleagues subjected the sonar data to greater scrutiny and confirmed dimensions of 20 feet (6 m).

Submersible investigations
Earlier submersible work had yielded dismal results. Under the sponsorship of World Book Encyclopedia, pilot Dan Taylor deployed the Viperfish at Loch Ness on 1 June 1969. His dives were plagued by technical problems and produced no new data. The Deep Star III built by General Dynamics and an unnamed two-man submersible built by Westinghouse were scheduled to sail but never did. It was only when the Pisces arrived at Ness that the LNPIB obtained new data. Owned by Vickers, Ltd., the submersible had been rented out to produce The Private Life of Sherlock Holmes, a film featuring a dummy Loch Ness Monster. When the dummy monster broke loose from the Pisces during filming and sank to the bottom of the loch, Vickers executives capitalized on the loss and 'monster fever' by allowing the sub to do a bit of exploring. During one of these excursions, the Pisces picked up a large moving object on sonar 200 feet (60 m) ahead and 50 feet (15 m) above the bottom of the loch. Slowly the pilot closed to half that distance but the echo moved rapidly out of sonar range and disappeared.

"Big Expedition" of 1970
During the so-called "Big Expedition" of 1970, Roy Mackal, a biologist who taught for 20 years at the University of Chicago, devised a system of hydrophones (underwater microphones) and deployed them at intervals throughout the loch. In early August a hydrophone assembly was lowered into Urquhart Bay and anchored in 700 feet (215 m) of water. Two hydrophones were secured at depths of 300 and 600 feet (180 m). After two nights of recording, the tape (sealed inside a 44 imperial gallon (55 US gal/200 L) steel drum along with the system's other sensitive components) was retrieved and played before an excited LNPIB. "Bird-like chirps" had been recorded, and the intensity of the chirps on the deep hydrophone suggested they had been produced at greater depth. In October "knocks" and "clicks" were recorded by another hydrophone in Urquhart Bay, indicative of echolocation. These sounds were followed by a "turbulent swishing" suggestive of the tail locomotion of a large aquatic animal. The knocks, clicks and resultant swishing were believed to be the sounds of an animal echo-locating prey before moving in for the kill. The noises stopped whenever craft passed along the surface of the loch near the hydrophone—and resumed once the craft reached a safe distance. In previous experiments, it was observed that call intensities were greatest at depths less than 100 feet (30 m). Members of the LNPIB decided to attempt communication with the animals producing the calls by playing back previously recorded calls into the water and listening via hydrophone for results, which varied greatly. At times the calling patterns or intensities changed, but sometimes there was no change at all. Mackal noted that there was no similarity between the recordings and the hundreds of known sounds produced by aquatic animals. "More specifically," he said, "competent authorities state that none of the known forms of life in the loch has the anatomical capabilities of producing such calls."

Robert Rines's studies (1972, 1975 and 2001)
In the early 1970s, a group of people led by Robert H. Rines obtained some underwater photographs. Two were rather vague images, perhaps of a rhomboid flipper (though others have dismissed the image as air bubbles or a fish fin). The alleged flipper was photographed in different positions, indicating movement. On the basis of these photographs, British naturalist Peter Scott announced in 1975 that the scientific name of the monster would henceforth be Nessiteras rhombopteryx (Greek for "The Ness monster with diamond-shaped fin").[49] Scott intended that this would enable Nessie to be added to a British register of officially protected wildlife. Scottish politician Nicholas Fairbairn pointed out that the name was an anagram for "Monster hoax by Sir Peter S".[50][51]

The underwater photos were reportedly obtained by painstakingly examining the loch depths with sonar for unusual underwater activity. A submersible camera with an affixed, high-powered light (necessary for penetrating Loch Ness' notorious murk) was deployed to record images below the surface. Several of the photographs, despite their obviously murky quality, did indeed seem to show an animal resembling a plesiosaur in various positions and lightings. One photograph appeared to show the head, neck and upper torso of a plesiosaur-like animal. A rarely publicized photograph depicted two plesiosaur-like bodies. Another photo seemed to depict a horned "gargoyle head", consistent to that of several sightings of the monster. Some believe the latter to be a tree stump found during Operation Deepscan.[citation needed]

A few close-ups of what is to be the creature's supposed diamond-shaped fin were taken in different positions, as though the creature was moving. But the "flipper photograph" has been highly retouched from the original image. The Museum of Hoaxes shows the original unenhanced photo. Charlie Wyckoff claimed that someone retouched the photo to superimpose the flipper, and that the original enhancement showed a much smaller flipper. No one is exactly sure how the original came to be enhanced in this way.

On August 8, 1972, Rines' Raytheon DE-725C sonar unit, operating at a frequency of 200kHz and anchored in Ness at a depth of 35 feet (11 m), identified a moving target (or targets) estimated by echo strength to be 20-30 feet (6-9 m) in length. Specialists from Raytheon, Simrad (now Kongsberg Maritime), and Hydroacoustics, Inc.; Marty Klein of MIT and Klein Associates (a producer of side scan sonar); and Dr. Ira Dyer of MIT's Department of Ocean Engineering were all on hand to examine the data and come to this conclusion. Further, P. Skitzki of Raytheon suggested that the data showed a protuberance, 10 feet in length, projecting from one of the echoes. Mackal proposed that the shape was a "highly flexible laterally flattened tail" or the misinterpreted return from two animals swimming together.

In 2001, the Robert Rines' Academy of Applied Science videoed a powerful V-shaped wake traversing the still water on a calm day. The AAS also videotaped an object on the floor of the loch resembling a carcass, found marine clam-shells and a fungus not normally found in fresh water lakes, which they suggest gives some connection to the sea and a possible entry for Nessie.

In 2008, Rines expressed his fear that the monster may have become extinct, citing the lack of significant sonar readings and a decline in eyewitness accounts. Rines plans on one last expedition to look for remains of the monster before he gets too old.

Operation Deep Scan (1987)
In 1987, Operation Deepscan took place - the biggest sonar exploration of Loch Ness. Twenty-four boats equipped with sonar were deployed across the whole width of the lake and they simultaneously sent out acoustic waves. BBC News reported that the scientists had made sonar contact with a large unidentified object of unusual size and strength. The researchers decided to return to the same spot and re-scan the area. After analysing the SONAR images, it seemed to point to debris at the bottom of the lake, although three of the pictures were of moving debris. Shine speculates that they could be seals that got into the lake, since they would be of about the same magnitude as the objects detected.

Darrell Lowrance, sonar expert and founder of Lowrance Electronics, donated a number of sonar units used during Operation Deepscan. After examining the echogram data, specifically a sonar return revealing a large moving object near Urquhart Bay at a depth of 600 feet (183 m), Lowrance said: "There's something here that we don't understand, and there's something here that's larger than a fish, maybe some species that hasn't been detected before. I don't know."

Discovery Loch Ness (1993)
In 1993 Discovery Communications began to research the ecology of the loch. The study did not focus entirely on the monster, but on the loch's nematodes (of which a new species was discovered) and fish. Expecting to find a small fish population, the researchers caught twenty fish in one catch, increasing previous estimates of the loch's fish population about ninefold.

Using sonar, the team encountered a kind of underwater disturbance (called a seiche) due to stored energy (such as from a wind) causing an imbalance between the loch's warmer and colder layers (known as the thermocline). While reviewing printouts of the event the next day, they found what appeared to be three sonar contacts, each followed by a powerful wake. These events were later shown on a program called Loch Ness Discovered, in conjunction with analyses and enhancements of the 1960 Dinsdale Film, the Surgeon's Photo, and the Rines Flipper Photo.