No-one knows why some kinds of coral are fluorescent.
Once a year, under very bright, blue lights, their mass spawning looks like a spectacular underwater hurricane of blazing dots and ribbony fibres, offset by the ocean's deep black.
Next week the magic of it will play out on the domed ceiling screens of the world's planetariums - Wollongong's among them - as part of a film timed to pre-empt the transit of Venus.
The film's creator Lynette Wallworth, an "immersive installation" artist from Sydney, sees clear links between the goings-on of the ocean - "a community as complex as our own ... and one at great risk of warming sea temperatures" - and the spirit of international co-operation that accompanied efforts to trace the 1761 and 1769 transits of Venus.
"That problem required more than one country working on it and ... today we are faced with challenges of the same nature, like global warming ... and the impact on coral reef systems," Wallworth said.
"Its seems eminently appropriate to link [global warming] to this rare astronomical event which has a precedent of global co-operation at its heart."
The film, Coral Rekindling Venus, will play in 25 full-dome digital planetariums worldwide next Tuesday.
The planetariums are normally reserved for astronomical events but Wallworth believes the immersive quality is perfectly suited to underwater scenes.
"It's a little like you've floated to the sea floor and are watching the most incredibly remarkable creatures passing above you. It's all real."
Some of the footage is taken from the open waters off Wakatobi in Indonesia.
The cameras get down among electric blue slugs with fire engine red mohawks; a psychedelic red seahorse; a complex network of ruby fronds curling poetically in on themselves and the undulating fluoro tail of a fish in retreat.
Microscopic images have been contributed by the University of Western Sydney's Dr Anya Salih.
Wallworth's other collaborators include Anthony Hegarty, lead singer of the 2005 Mercury Music Prize-winning band Anthony and the Johnsons, who wrote the song Rise especially.
A 22-minute version of the film (the full length is 45 minutes) will be shown at the Wollongong Science Centre and Planetarium on June 5 from 7pm. The presentation includes a second film on the transit of Venus, which will occur on June 6. The film costs $8. Inquiries: 4286 5000.
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