|The Long answer is:
Nobody knows for sure if Nessie is real. Thousands of people have seen her over the past 1500 years. But proof in the scientific sense of the word proof has not yet been recorded.
Today, even a photograph would not be considered proof because it is too easy alter a photograph. Jan Sundberg tried to trap Nessie so he could obtain a DNA sample, but she didn't swim into his trap.
Nessie is not the only lake monster in the world. I have met people whom I believe when they tell me they personally saw a lake monster. But the human eye can be fooled, too. If you've ever studied optical illusions, you'll see what I mean.
Jan Sundberg thought he had recorded Nessie once, but upon further investigation, he had recorded a small earthquake at the bottom of Loch Ness, where there is an active earthquake fault line Jan spends a lot of time at Loch Ness looking for Nessie because he believes she exists. Jacques Boisvert scuba dives every day in Lake Memphremagog in Canada because he believes that lake has a monster.
Belief is not proof. Lack of scientific evidence is not proof that there is no Nessie. My personal belief is that several different kinds of large creatures live in Loch Ness and that within the next decade we will have scientific proof.
Here is a page with many photographs that people have said were Nessie:
The man who owns this website thinks all the photographs except the one that he himself took are not Nessie.
Here is a website (click the blue links) that shows many mistaken photos of Nessie:
William Hill awards for Nessie photos:
As of today, it is only possible to say that many people believe they have seen Nessie. We will have to wait for more scientific proof.