tim dinsdale devoted his life to answering this question. >> he first went up in april 1960, and everyear thereafter he went to find loch ness every year thereafter, he went to loch ness. from the end of 1960s, he'd given up his work and job and was doing this full-time. >> but he never captures nessie as clearly as he did in 1960. there have been other photos and films, but the dinsdale footage remains iconic. >> i often say witnesses seldom lie. cameras very often do. sometimes without their owner's knowledge. the dinsdale film of 1960, it's quite a poor quality film, which makes identification difficult. >> my father's film, to this day, stands as being unexplained. but i think -- i'm convinced -- that given all the estsdz, all the eyewitness testimony, all the photography and my father's film and other film taken that there's something large living in loch ness. >>> coming up -- >> bigfoot turns, looks at the camera, and is gone. >>> a myth centuries old. >> bigfoot appears out of the bushes and makes those long, striding steps. >> and the iconic film that became part of the legend