Prove the DNA came from Nessie.
Ted Holiday's "The Great Orm of Loch Ness" will give it a run for its money. His theory was is was a giant prehistoric slug known as the Tullimonstrum Orm.
The reason he came to that conclusion is that before WWII, when that region of Scotland was all the more inaccessible, and very few ever got up that way to disturb Nessie's peace, she occasionally was sighted on land. Even walking across the road. And they found "bedding sites" on the shore of the loch, like where a deer would bed down, except all the grass had turned brown. And it was Holiday theory that this was because slugs make slime, and this particular slug's slime was toxic to the grass.
https://en.wikipedia.org/wiki/Tullimonstrum
But Holiday fails to mention until the final pages of the book that not only was the tullimonstrum orm extinct, the largest fossil yet discovered was only 18 inches long.
The last DNA tests they ran on Loch Ness said they found large amounts of eel DNA in the water.
the white blob in the photo clearly shows ancient aliens