Yes, this is a legit thing.
The organizers of the Loch Ness Marathon (which is apparently a thing also) have come up with a new way to get publicity for the event. The have offered $75,000 to anyone who can get a selfie - with the Loch Ness Monster. Good luck with that.
I do think this is a pretty cool way to try to get people to participate in the event. The article about the event gives a short history of Nessie, saying how it was first seen in 565 A.D.. And,(anyone else remember this?) last year people were saying Nessie died. Did she? No. Even if one Nessie died, there would still be others, because there has to be a breeding population in the Loch, unless, of course, there isn't.