Lochness Monster.
A local pay channel has the slogan: "If there's magic out there we'll find it."
For this commercial it had to seem as though Nessy had been captured for the first time on film, perfectly framed in a moody misty Scottish setting with only a few ripples disturbing the water, and all corresponding with a lunar eclipse. (Thank goodness for computer graphics.)
The hardest part was the getting the scene to have a 'big' feel and to handle the layers of fog in an economical way.