Earth News, BBC (October 29, 2009)
"One of the most elegant courtship rituals in the animal kingdom has been captured on film by a BBC crew.
"The dance of the weedy sea dragon takes place every year in the shallow seas off the coast of Australia.
"During the ghostly dance, two beautifully odd-looking fish mirror each other's every movement...."
The article's text and two gives a bit of extra information about weedy and leafy sea dragons, and where the footage was taken.
The main attraction of this page is the video: 3:57 of narration and music over some quite good nature photography. I'd have preferred that more clues as to the size of the fish appear - but this is a good piece of nature documentary.
And Now, for Something Not Completely Different"Weedy Sea Dragon"
thelning, YouTube (December 23, 2008)
"The weird and wonderful weedy sea dragon. Filmed at Jervis bay, NSW, Australia 1986. You can see at the end of the video how well camouflaged the weedy sea dragon is, which makes it difficult to find them."
The YouTube video has no sound, and isn't as elegantly edited as the the BBC video. On the other hand, about halfway through you see a weedy sea dragon with a diver - which shows the size of these odd-looking creatures.
A tip of the hat to therightblue, on Twitter, for the heads-up on the BBC article.