Coral's sex life is not particularly spontaneous. Marine biologist and cinematographer Richard Fitzpatrick has been watching coral spawn for 25 years and said he knew when to capture the, er, motion in the ocean.
"The big days are after the full moon in November," he told The Huffington Post Australia.
"On the third day after the full moon, you'll get the staghorn corals spawning, but the really big night is usually five days after the moon. That's when you get the big plate corals spawning and a lot of other corals."
This year, the auspicious fifth day was also a time of terrible weather.
"The conditions were horrendous but Sunlover Cruises has a massive pontoon out there and they've got a lovely coral garden out front so we asked if we could go there," he said.
"The wind was probably blowing about 25-30 knots but the pontoon gave us a good solid base."
Fitzpatrick and his company Biopixel filmed much of the footage for Sir David Attenborough's Great Barrier Reef, including the tiger shark scenes, and said a coral spawning sequence could take years.
"It only happens for such a short amount of time that one year, you'll do the wide-angle shots, then the next year, you'll do all the mids. If the weather's bad, you'll have to wait another year to finish it."
How has coral bleaching affected this year's spawning?
Researchers are assessing this year's coral spawn after last summer's devastating coral bleaching event.
While reefs off Cairns, like where Fitzpatrick filmed, looked healthy, ARC Centre of Excellence for Coral Reef Studies professor Andrew Baird told the ABC his colleagues had trouble finding any evidence of a spawn up north.
"Eighty to 90 per cent of the corals in the shallows at Lizard Island were killed by the bleaching so there's just a lot fewer corals," Baird told the ABC.