pretty big and it was shifting. >> and that legend has been kept alive largely by one mysterious piece of film shot more than half a century ago. >> my father took a film in 1960 of some object in loch ness. and that pretty much changed his life. changed my life. >> april 1960, loch ness, scotland. armed with a rented 16-millimeter camera, british aeronautical engineer tim dinsdale is monster hunting. >> he read an article in 1959 in a small magazine and became fascinated by the subject. the article covered things like a surgeon's photograph and dozens of other people's eyewitness testimony. >> the 1930s and '40s saw a surge in apparent loch ness monster sightings, including this one filmed by malcolm irvine. dinsdale wanted in on the action. >> so he went up there and his goal was to get unequivocal moving film. on his first trip, he got a sequence of film. >> on his fourth day at the lake, tim captures what thousands before and since have tried and failed to film. >> he described it as for all well being like the back of an african buffalo. same color tone. quite an enormous -- quite a