Coral Spawning Great Barrier Reef 2026 | Ocean Universal
The Great Barrier Reef's coral spawning is one of the largest reproductive events on the planet. Every year, usually after the November and December full moons, corals across the reef release eggs and sperm into the water at roughly the same time. If you're in Cairns and you dive at night during the right window, you can watch it happen.
We've been helping FNQ divers prepare for spawning season for over 25 years — first as Spearfishing Superstore, now as Ocean Universal. Here's what you need to know.
What is coral spawning?
Coral spawning is the mass release of egg and sperm bundles by reef-building corals. On the Great Barrier Reef, hundreds of coral species participate in what researchers call a "mass spawning event." The bundles float to the surface, where fertilisation occurs. Successful larvae eventually settle on the reef and grow into new coral colonies.
The phenomenon was first documented in 1981 by researchers from James Cook University studying reefs near Magnetic Island, just off Townsville. Before that, nobody knew corals spawned this way. Since then, the annual event has drawn marine biologists, underwater photographers, and divers from around the world to Far North Queensland.
According to the Great Barrier Reef Marine Park Authority, the spawning is triggered by a combination of water temperature, tidal patterns, and lunar cycles. Most species spawn at night, between roughly 7:30pm and midnight.
2026 predicted spawning dates
Coral spawning on the GBR typically occurs 4 to 6 nights after the full moon in November and December, when sea surface temperatures sit above 27°C.
The 2026 full moon dates are:
- November 17, 2026 (Tuesday)
- December 16, 2026 (Wednesday)
Based on these dates, the predicted spawning windows are:
Primary spawning (outer reef): November 21–25, 2026
Secondary spawning: December 20–24, 2026
Different species spawn on different nights. The November window usually sees the biggest mass event on the outer reefs, while December often involves different coral groups. Inshore reefs near Cairns can also see spawning activity after the October full moon (October 18, 2026).
Note: These are predictions based on moon phases. Actual timing depends on water temperature, weather conditions, and the specific reef. We update this page each year as more information becomes available from local dive operators and researchers.
How coral spawning works
Most reef-building corals are hermaphrodites — each polyp produces both eggs and sperm. During a spawning event, polyps release small bundles containing both, which float to the surface. The bundles break apart, and cross-fertilisation happens between different colonies of the same species. This genetic mixing is important for reef health and resilience.
Research from the Australian Institute of Marine Science shows that fertilised eggs develop into larvae called planulae within about 12 hours. These larvae drift in ocean currents for days or weeks before settling onto hard substrate and starting to grow. Only a tiny fraction survive — but given the billions of eggs released across the reef, the numbers add up.
The timing is precise for a reason. By spawning together in massive numbers, corals overwhelm predators that would otherwise eat most of the eggs. The synchronised release happens at night, which further reduces predation from visual feeders like fish.
What it looks like underwater
Divers describe it as an underwater snowstorm, but in reverse — the bundles rise from the coral rather than fall. In the beam of a dive torch, you can see thousands of small pink, orange, or white spheres drifting upward. The water becomes thick with spawn, and visibility drops as the event intensifies. It looks nothing like a normal night dive.
The event usually builds slowly. Early in the evening you might notice a few bundles here and there. As conditions align — usually between 8pm and 10pm — entire sections of reef release simultaneously. On a good night, the water column fills with spawn from the reef floor to the surface.
Some divers also report a faint sweet or musky smell at the surface, especially near shallow reefs. The whole experience is unlike anything else you'll see on the GBR.
Where to see coral spawning from Cairns
Cairns is one of the best launch points for coral spawning dives. The outer reef is accessible by liveaboard or fast boat, and several local operators run dedicated spawning trips each year.
Outer reef sites: Agincourt Reef, Ribbon Reefs, and Opal Reef typically see the strongest spawning events. Water temperatures reach 27°C+ earlier on the outer reef, which is why the November mass event tends to happen there first.
Inshore reefs: Green Island, Fitzroy Island, and the Frankland Islands can also see spawning, though sometimes on a smaller scale. Inshore reefs may spawn after the October full moon — a few weeks earlier than the outer reef.
Operators to look for: Reef Encounter, Pro Dive Cairns, and Mike Ball Dive Expeditions all run spawning-focused trips during the predicted windows. Spaces fill quickly, so booking well ahead is worth it.
If you're not sure what gear you need for a night dive on the outer reef, pop into our Westcourt store and we can sort you out.
Night diving gear for coral spawning
A spawning dive is a night dive in particle-dense water. That changes what gear you need compared to a standard night dive on the reef.
Dive torches
Your primary dive torch needs to cut through spawn-filled water. Look for at least 1,200 lumens with a wide beam angle. A narrow spot beam won't show you much when the water is thick with eggs. Battery life of 3+ hours is important — spawning can go on for a while, and you don't want to miss the peak because your torch died.
Bring a backup torch. Always. A small wrist-mounted light works well as a secondary. Chemical glow sticks are old school, but they don't run out of battery and they help your buddy find you in spawn-clouded water.
Camera gear
If you're shooting photos or video, the biggest challenge is backscatter. All those floating particles reflect light straight back at your lens. A red filter helps reduce this. Wide-angle lenses capture the scale of the event better than macro. Make sure your underwater camera housing is rated for the depth you'll be diving — the outer reef sites can be 15-25 metres.
Wetsuits
November and December water temperatures around Cairns sit between 27-29°C. Most divers are comfortable in a 1.5-2mm wetsuit or even just a rash vest. But if you're doing multiple night dives, you might get cold sitting on the boat between dives. A 2-3mm shorty or full suit gives you some flexibility.
Dive computers and safety
A dive computer with a backlit display is essential for night diving. Check your battery before the trip. Bring a surface marker buoy (SMB) — on a dark night with reduced visibility, your boat crew needs to see you when you surface.
It's not just corals
The coral spawning event triggers a broader reproductive response across the reef. According to Queensland Museum researchers, sea cucumbers, soft corals, sponges, and some species of worms and clams also spawn around the same time. The whole reef comes alive.
Fish behaviour changes too. Many species feed heavily on the spawn — you'll see parrotfish, surgeonfish, and other reef fish gorging on eggs and bundles. Manta rays have been observed filter-feeding in spawn slicks on the surface. It's a food chain event as much as a reproductive one.
For a full rundown of GBR marine life terminology, check out our diving and spearfishing glossary.
Tips from 25 years of spawning season
- Book early. Dedicated spawning trips sell out. Operators start taking bookings months in advance.
- Multiple nights. The spawning doesn't always peak on the first predicted night. Booking a liveaboard for 2-3 nights gives you the best chance of seeing the main event.
- Test your gear. Run your torches, check camera housings, replace old batteries. Don't find out something's not working on the boat at 8pm.
- Go wide, not macro. The spectacle is the scale of it. Wide-angle captures that better than close-up shots of individual bundles.
- Stay warm between dives. Bring a dry towel and something to layer over your wetsuit. December nights in Cairns are warm, but you cool down quickly after a dive.
- Check conditions. Strong wind or rain can affect visibility and boat access. Check the Bureau of Meteorology Cairns forecast in the days leading up to your trip.
Coral spawning and reef health
Coral spawning isn't just a spectacle — it's how the reef rebuilds. After coral bleaching events, the larvae produced during spawning are what repopulate damaged areas. The GBRMPA's Reef 2050 Plan identifies natural recruitment through spawning as a key factor in reef resilience.
Research from the Australian Institute of Marine Science has shown that spawning success varies from year to year depending on water temperature, cyclone activity, and crown-of-thorns starfish populations. In good years, billions of larvae are produced. The reef's ability to recover from bleaching and storm damage depends heavily on these annual spawning events.
If you want to understand more about the reef's current condition, the AIMS Long-Term Monitoring Program publishes regular updates on coral cover and reef health.
Frequently asked questions
When does coral spawning happen on the Great Barrier Reef?
The main mass spawning event typically occurs 4 to 6 nights after the full moon in November, with a secondary event after the December full moon. In 2026, the predicted windows are November 21–25 and December 20–24. Inshore reefs may also spawn after the October full moon.
Can you see coral spawning while snorkelling?
Snorkelling over shallow reefs during spawning is possible, but visibility is limited at night without a torch. Most people see it best on a guided night dive. Some operators offer snorkel-friendly spawning trips on shallow reef sites near Cairns.
What time of night does coral spawning happen?
Spawning usually begins around 7:30-8:00pm and can continue until midnight. The peak is often between 8pm and 10pm, though it varies by species and conditions.
Do I need a night diving certification?
Most dive operators require at least an Open Water certification for supervised night dives. An Advanced Open Water certification with a night dive specialty is preferred. If you're not night dive certified, some operators offer guided experiences for less experienced divers.
What gear do I need to watch coral spawning?
At minimum, you need a reliable dive torch (1,200+ lumens recommended), backup light, and your standard dive gear. A camera with underwater housing is optional but worth it. We stock everything you need at our Westcourt store.
How long does coral spawning last?
Individual corals release their bundles over a few minutes, but across a reef, the event can last several hours in one night. The entire spawning period spans multiple nights as different species spawn on different evenings. The full window is usually 3-5 nights.
Gear up for spawning season
If you're planning to dive the 2026 coral spawning, sort your gear out well before November. Night diving torches, camera housings, and backup lights are the first things to sell out as the season approaches.
We're at Shop 1/310 Mulgrave Road, Westcourt — open Monday to Friday 9am-5pm, Saturdays 9am-3pm. Our team has been through more spawning seasons than we can count, and we're happy to help you find the right gear for your experience level.
Ocean Universal — formerly Spearfishing Superstore. Built for Divers, BY DIVERS.
Phone: (07) 4036 2080