Flash mobs are supposed to be spontaneous, synchronised and impressively put together.
Graduates of the Royal Navy School in Stavanger, Norway went for uncoordinated and charmingly awkward in their passing out ceremony, below.
They start off in formation, and everything looks serious and solemn, when the first few notes of Mark Ronson's Uptown Funk comes on, and somebody at the back loses his hat.
Some fantastic solo dance moves follow...
And a clear leader is established...
And then it's all over in a flurry of cheers and hat-throwing, as the rest of the navy watches on. Is it confusion? Shock? Horror?