I believe that the Loch Ness Monster existed. The problem is trying to explain a creature and behaviour that fits the evidence for and against its existence. Mainly, why are there many "sightings" of giant moving creatures on sonar, but when the BBC performed a full search of the Loch, using over 600 separate sonar beams and satellite tracking - a combination that could pick up a small buoy - why was there no significant sightings?
There are obviously a lot of hoaxes surrounding the Loch Ness Monster, and a lot of evidence has been ruled out, so I'll try to decipher as best I can:
Firstly - What.
A fool would believe that there is only one creature in there that produces the evidence that we have. A fool would also believe that Nessie is a plesiosaur left over from the Cretaceous period. If there were plesiosaurs living in the Loch, there would be multiple sightings daily as they would have to surface to breathe. Also, Loch Ness is only 10,000 years old, and was a solid ice cube for 20,000 years before that. Plesiosaurs also couldn't live in such frigid waters as they would be cold-blooded. So not a plesiosaur.
I believe the evidence shows that the "monsters" are (or were) particularly large amphibious creatures (a hypothesis which has been supported by experts R.T. Gould and Roy Mackal) - possibly resembling the physiology of a large newt. It has been argued that the creatures sighted could be giant eels, but as they move in an undulating sideways motion they don't fit the sonar evidence.
Secondly - How are they spotted so many times, but not one significant hit in 2003?
I believe that these creatures have unfortunately perished. Although there is a lot of evidence to suggest that there was a significant connection between Loch Ness and the North Sea, nowadays, it's unlikely for such an animal to migrate unnoticed. The northern waterways from Loch Ness to the North Sea are indeed large enough to allow the migration of hundreds of five-foot pike and salmon every season, so it is possible for them to support quite large animals. But there is still hope.
The problem with the Loch is that it is horribly murky - you can only see the top five feet of a Loch that is (at its maximal) 40km long, 2.4km wide, and 250m deep. As such, the only evidence that can be taken is sonar.
Now, the evidence.
The contemporary interest in the Loch Ness Monster began on July 22, 1933, when George Spencer and his wife spotted a large animal cross the road 20m in front of their car, leaving broken undergrowth in its wake. They described the creature as having a long neck, about 3m long, extended from a large body approximately 1m high and 8m long. They reported seeing no limbs - this has been discussed in the media as proving the depiction of a plesiosaur-like creature, but the report also notes that the couple couldn't see the lower portion of the body due to a dip in the road. Such sightings, with precise descriptions of similar creatures continued throughout that year, and sporadically through to 1963 where the first video footage was released.
Unfortunately, as it was taken at a distance of 4km, it is quite poor quality, but does indeed show an animate object that fits the dimensions described in early accounts:
The periodic nature of the sightings between 1933 and 1963 could be the result of migrational movements through the waterways explained earlier. The sightings became frequent enough to prompt the creation of hunting parties determined to capture the creature "dead or alive", and in 1938, the Chief Constable (William Frasier) wrote a letter declaring that he had no doubts that the creatures existed and believed that he was unable to protect the "monsters" from such parties.
In 1943, a member of the Royal Observer Corps reported seeing a creature some 230m away from his boat. He also described a long body, about 6m long, with an extended neck that protruded about 1.5m out of the water. The theory of an amphibious creature helps to explain this encounter but also explains why there may not be as many as if the creature required air like a marine mammal (or a plesiosaur).
In 1954, the fishing boat Rival III spotted sonar readings of a large object keeping pace with the boat some 150m below. The large object followed the boat for about 800m before disappearing behind the boat, only to appear some time later. Although there were many sonar reports before this, the Rival III's encounter was the first conclusively positive sonar report of such a creature.
In 1960, Tim Dinsdale used a primitive 16mm camera to film a "hump" crossing the water with a powerful wake for approximately four minutes. This film was repudiated by sceptics, as it was claimed that if the contrast was increased, the hump is simply a boat, with a man clearly seen on board. However, in 1993, Discovery Communications made the documentary Loch Ness Discovered where they digitally enhanced the Dinsdale Film. The computer expert's analysis found the outlines of the rear body, rear flippers and two additional humps of the body.
In 1968, the Loch Ness Phenomena Investigation Bureau (LNPIB) introduced a two-week trial where they used sonar transducers to create a sonar "net" across a section of the Loch to see if any animate objects passed through the area. They reported multiple 6m long animate objects travelling in a distinct propulsion motion, ascending from, and descending to the Loch floor. These objects reached speeds of 10 knots (19 km/h) and the fact that they rose and descended so rapidly implies that they are animals, rather than just abnormally large fish.
In 1969, the LNPIB performed another examination, this time in a sweep formation. They followed a 6m long moving object for approximately three minutes.
In 1969, a team from the World Book Encyclopaedia attempted to use a submersible to track the sonar hits from earlier expeditions. The Pisces picked up a large moving object on sonar 60m ahead of the craft, about 15m above the Loch floor. The pilot closed to half that distance (30m) but the echo moved rapidly out of sonar range and disappeared.
In 1970, the biologist Roy Mackal used hydrophones (underwater microphones) to monitor the length of the Loch. "Bird-like chips" were heard by the hydrophones, with the deepest ones (set at 180m) showing that many of the sounds came from a deeper source. Later recordings revealed "knocks and clicks" followed by "turbulent swishing" sounds, suggesting the tail-locomotion of a large animal. Interestingly, the noises stopped whenever a craft passed over or near the hydrophones.
In 1972, Robert H. Rines, a lawyer, inventor, researcher, and composer, looked out his friend's window and allegedly saw the creature powering across the Loch. He, his wife, and his friends were convinced. Mrs Rines said to her husband, "You need to find that animal again, no matter how long it takes." Thus began this brilliant man's lifelong quest.
Later in 1972, Rines tried to capture a photograph of the creatures to see if the animals producing the sounds in Mackal's experiments were the same as those on the sonar. He attached submersible cameras with high-powered floodlights, capable of piercing the ludicrously murky deep Loch water, just enough to produce a vague image of a close object. When the submersed devices picked up an echo on sonar, the floodlights would be hit and a picture taken. This is the result:
In 1972, Rines performed more sonar sweeps, finding several 6-9m moving objects. This time the more advanced Raytheon DE-725C was able to pick up disturbances projecting from the rear of the objects. These 3m long rapidly moving echoes suggested "highly flexible laterally flattened tails" used for the tail-locomotion implied in the hydrophone experiments.
Unfortunately, this is where the more conclusive sonar echoes begin to fade away.
In 2001, Rines' team found marine clam-shells and fungi that aren't usually found in fresh-water. This suggests that the connections from Loch Ness to the ocean could still be intact and it is possible that such waterways could support the migration of larger animals.
In 2008, Rines declared that due to a lack of recent recordings and the effect of global warming, he believed that the creatures in the Loch were unable to adapt to the warming waters of the Loch and had died. Rines then turned his attention to sweeping the Loch's floor for animal remains in the hopes of finding proof of the creatures' existence. He managed to inspect only 5 of his 100 locations of interest until he died on November 1, 2009.
When once asked about his work and his sceptics, Rines replied, "Admiral Peary had to make 28 trips before he got to the North Pole. What am I to do, forget what I saw?"
God bless that man.
So. In conclusion. I'm convinced large creatures roamed Loch Ness. These creatures were approximately 6m in length with long necks and long tails (which were used for locomotion). I believe the creatures either moved out of the Loch into the North Sea, or have unfortunately died. For some reason I'm really not that fussed whether the finding of a large animal carcass will ever come to be, and the existence of such animals will be conclusively proven - or not.
I'm just a man possessed by an idea.
Submersed Ethan..