Was the Bucc in the film painted white? XN954, an S1 (thank you, Tim Laming for refreshing my memory...) was pitched over the side of Ark Royal in April 1974 for a safety film (the S1 being out of service by that point, of course).
I haven't seen said film in toto, but have seen a white painted Bucc going over the side of Ark right at the end of the FAA museum's 'Carrier' Exhibit - I'm assuming that this is taken from the safety film, and making the further assumption that there is only one film of a Bucc going backwards off the deck!