Holy cow, I wrote a book!
Scotland doesn't have the corner on monsters in lakes. You'll also find them in Norway, in Sweden (read about a recent expedition), and in Canada, among many, many others. Anywhere there are lakes, there's bound to be a legend about a monster in one of them.
It appears, however that Sweden's Storsjöodjur is about to lose its protected species status, owing to an inquiry inspired by a man's request to harvest the creature's eggs so he can hatch them.
As a result, it will soon be open season on Storsjöodjuret. Happy hunting.
(I find the Swedish word odjur somewhat poetic. It translates as "monster" but literally means "un-animal".)