Perhaps they should go and see the movie at the Original. There's speculation, scenery, and a good collection of eyewitnesses. Exactly the sort of people that Agatha Christie warns us not to trust. And how right she was. The Loch Ness story is a handbook of human error, more damaging to the notion of eyewitness evidence than Johnnie Cochran.
Some people see what they want to believe.
An otter becomes a monster's neck, a wave a plesiosaur's wake. Others just make it up. Baron Muenchausen should have settled in Drumnadrochit. He'd have found plenty of hoaxers only too pleased to lend his tales a hand. Or so says one confession.