In the past, searches have been conducted for Nessie, the Loch Ness Monster, using technologies ranging from men with binoculars to underwater video cameras and sonar.
A new search being led by a kiwi scientist, Professor Neil Gemmell from Otago Uni, will take hundreds of samples from deep in the lake and test them for DNA. The DNA that is sequenced will be compared to samples in a database of known species, and unknown creatures like nessie will show up as unmatched. Even without a match the scientists will be able to work out how closely related new finds are to existing species, which will help them to know what kind of creatures have been indirectly found.
The Loch Ness monster is an interesting case. Modern belief in the monster started around 80 years ago with images and stories of a monster from well meaning people. One image may well have been of the photographer's dog taking a swim.
However, things changed in 1934 when a famous "surgeon's photograph" was published, taken by a gynaecologist. This was a departure from previous sightings because it has subsequently been shown to have been a deliberate fake. The photo was revenge on the Daily Mail, which had previously ridiculed one of its employees for believing in a hoax consisting of faked footprints. In revenge, the employee worked with family members to cover a toy submarine with wood putty in the shape of a head and back of a creature like a plesiosaur, and then took pictures of it before giving them to a friend who had them developed and sold them to the Mail.
After this photo, several fakes were attempted, alongside some pictures and video that seem to have been a genuine case of mistaken identity. Fakes included one called the Loch Ness Muppet because it was so badly done, fake footprints made by a hippopotamus umbrella stand and a shaved elephant seal.
I guess this follows other cryptids (supposed animals unknown to science) like bigfoot, where initial mistaken sightings eventually give way to professional fakers who are out to make money from their stories, footage, and decomposing remains.
People's continued belief in the monster, despite the lack of solid evidence, shows how much people want to believe in fantastical stories.
It's interesting that most of the expeditions to find nessie have ended up being "inconclusive" - the results have always been negative, but stories about the work usually stress how this isn't proof that the monster doesn't exist. Maybe this helps with local tourism, and I guess nobody wants to be the person to ruin the legend for others.