GENUINE  FACTS
  about "NESSIE",
THE LOCH NESS "MONSTER" 
Dozens of books (bibliography here), hundreds of chapters, thousands of articles
have been written about Nessie since the 1930s.
The name "Nessie" and the Surgeon's Photo (above left)  are recognized everywhere. 
Almost everyone has the impression  that Nessie is, like Santa Claus, just a nice story for children as well as a great boost to the economy of the Highlands of Scotland.  Around Loch Ness itself, that impression is reinforced by Nessie-sighting tours and boat rides and by the innumerable Nessie trinkets on sale: Nessie logos on all sorts of souvenirs, toy Nessies in every size and shape and texture, postcards with every imaginable joke about Nessies and every sort of image of her: serpentine, or dragon-like,  or teddy-bear cuddly.
 The Loch Ness 2000 Exhibition  in Drumnadrochit conveys the view that
 people who think they see NESSIE are influenced by expectation and wishful thinking
and are really seeing a seal, or an otter, or a wave, or a boat wake, or a bird, or a deer,
or, the Exhibition's favorite, a very large sturgeon.

BUT  IN  FACT,  THERE  IS  STRONG  EVIDENCE
THAT  THERE  REALLY  ARE 
LARGE,  YET-TO-BE-IDENTIFIED  ANIMALS
IN LOCH NESS
Last updated: December 17, 2013
What my interest in Nessie has meant to me in a personal way is described in
Loch Ness OdysseySnowy Egret, 51 (#2, Autumn 1988) 8--15
The strongest evidence comes in three independent bits of objective data:
The Dinsdale film (above right is one frame from it)
The film can now be watched over the Internet at
http://www.themanwhofilmednessie.com/tims-nessie-film.html

That link is also on the website describing the biography of
Tim Dinsdale by his youngest son Angus:
The Man Who Filmed Nessie ---
Tim Dinsdale and the Enigma of Loch Ness
Many sonar echoes from large, moving, mid-water objects
obtained by many different expeditions since the 1950s using many different types of sonar
Underwater photos of a giant flipper simultaneous with huge sonar echoes
That evidence is discussed at length in my article,
"The Case for the Loch Ness Monster: The Scientific Evidence"
Journal of Scientific Exploration, 16(2): 225--246 (2002)
Among other points made in  this article, evidence is presented
that the "flipper" photos have not been "retouched" to show something
not present in the original photos. Charles Wyckoff, the photographic expert
on the Rines team points out that the only manipulation was to superpose
several transparencies filtered through different colors. Alan Gillespie, who did
this "computer enhancing" at Jet Propulsion Lab, pointed out
that the flipper shape can be seen in the original unenhanced transparency,
which was published in WILDLIFE, March 1976, article by Nigel Sitwell, "The Loch Ness Monster evidence", pp. 101-109.
The "retouching" allegation was first made in an article in DISCOVER magazine, which refused then to print Wyckoff's letter of protest, 
a copy of which is now available here.   
WHY  IS  THIS  STRONG  EVIDENCE  SO LITTLE KNOWN? 

Because the media continue to treat Nessie only as an amusing story.
The objective and strong evidence summarized in the above article is not properly presented in the "documentary" films and television programs about the subject. There have been at least 18 such programs (in English alone) since the 1970s. Typically they give the false impression that eyewitness reports are the main grounds for believing Nessies to be real. Often the strongest evidence is not even mentioned, and when it  is, it is often misrepresented.   For a detailed analysis of the 17 documentaries shown between 1972 and 2001, see my article,
 "Common Knowledge about the Loch Ness Monster"
Journal of Scientific Exploration, 16(3): 455--477 (2002)
I had published earlier analyses of the coverage that Nessie has received
in newspapers, magazines, and books:
Public Perception of the Loch Ness Monster, Scottish Naturalist, 1988, 69--93
The Loch Ness Monster: Public Perception and the Evidence, Cryptozoology, 1 (1982) 40--45

My book,
The Enigma of Loch Ness: Making Sense of a Mystery
University of Illinois Press, 1986
discusses how searching for Nessie is different from doing (professional) science. The book begins by showing how exactly the same evidence can be used to argue for and against the existence of Nessies. It is available as an AUDIO BOOK,  RC 25592 (1988).               REVIEWS are listed HERE.
Minor corrections were made in a 2nd printing, 1987
Some updating was done for the paperback edition, 1988.
The British edition, Johnston & Bacon 1991, omits the extensive bibliography without correcting the index accordingly.)
“SKEPTICAL”  MISINFORMATION  ABOUT  NESSIE
A critique of “Nessie, the Loch Ness Monster”, by Daniel Loxton
Chapter 4 in Abominable Science (Columbia University Press, 2013)