That to me looks like a VERY bad copy of the footage taken in Kent during 1942 of the bouncing bomb tests.
The bomb was created solely for use on one mission against German dams in the Ruhr, so wasdesigned to bounce across the water (initially hitting the
surface at just under 300mph and revolving at 500rpm) before hitting the dam wall, then rolling down it and exploding at it's base under the
water.
During tests the prototype bombs often came to pieces whilst bouncing (as seen in the film) - or just plain sank.
I've searched for footage online of the tests, but haven't yet found any. However, it has been featured in many documentarys on the subject, which
is where I'd guess this 'UFO' footage came from.
Here's a few bouncing bomb links.
aia.lackland.af.mil...
www.geocities.com...
news.bbc.co.uk...
www.spitfire-museum.com...