Once a year, the over 400 different types of Great Barrier Reef corals reproduce en masse, in an event known as Coral Spawning. Coral Spawning always occurs at night, with the release of the corals’ eggs and sperm tied to the moon’s presence, light and lunar cycles. In 2011, we witnessed the magic of Coral Spawning for the first time, with Cairns operator Tusa Dive. It was amazing! Diving amongst the thousands of pink eggs which floated through the water, like bubbles rising in a flute of champagne.

Our coral spawning trip commenced with a 5.45pm boarding time on Tusa Dive’s T6 boat, moored on E-Finger at Cairns’ Marlin Marina. The day – Thursday 17 November – the guests, an excited combination of 33 certified divers and 5 snorkellers – the event we were all hoping to see, the Great Barrier Reef’s annual Coral Spawning.

Skipper Adam welcomed us all aboard and advised that our destination for the night was a site known as ‘Coral Gardens’ at Saxon Reef, approximately 30 nautical miles (60 km) off the coast of Cairns. Tonight’s winds were forecast to be around 15 knots and he suggested that if anyone suffered from motion sickness, they should take advantage of the preventative pills on board. Adam then headed upstairs to prepare T6 for departure.

Tusa Dive’s Trip Director Jo then took the microphone and introduced us to our crew for the evening. There was about 1 crew member for every 4 guests aboard, making sure there was plenty of assistance. Jo went through the features of T6, Cairns’ newest reef tour boat, including its hot water showers. He provided a safety briefing and then went through the importance of the Great Barrier Reef as a marine park, protected for future generations.

Key messages included: look but don’t touch; watch your position in the water and avoid getting too close to the corals; take only photos and leave only bubbles.

While Jo ran through the night’s itinerary (dive – eat – dive) T6 made its way out of Cairns’ Trinity Inlet and commenced its 90-minute motor to Saxon Reef. During the trip out, a reef biologist presentation was provided by Stuart Ireland. Stuart explained that coral spawning on the Great Barrier Reef happened once a year, over a few nights. The spawning allowed for cross-breeding and hybridisation of the Great Barrier Reef corals, which assisted with evolution and helped the reef adapt to changes. Click here for more information on Coral Spawning.

Presentations complete, the guests dispersed across the two air-conditioned interiors (downstairs and upstairs saloon) with some choosing to watch the sunset from the top sundeck, which soon became the moondeck.

About 30-minutes before arrival, all divers were taken inside and given a dive and equipment briefing. There was the option of taking guided and unguided dives, with all divers provided with an underwater torch and glow sticks on their tanks. A top tip from the dive instructors: red eyes glowing back at you were from crustaceans, green eyes glowing in the night waters were from predators, including sharks and stingrays.

As Tusa Dive T6 moored on Saxon Reef, the divers geared up and prepared for their first night dive.

First Dive 8.10pm – Saxon Reef – Coral Gardens. Splashing down in the warm (27 degrees) water, we followed the mooring line down to explore the site. Large boulder corals greeted us on the ocean floor at around 12m: these corals had spawned two nights earlier, so we looking for the staghorn and mushroom corals tonight. Coral Gardens has several large “beds” of staghorn corals and as we explored the site, we noticed a few appeared to be ready to spawn, but no action as yet. Night diving is always an interesting experience, seeing many marine creatures that are not visible during the day. Some of the highlights of this dive included seeing several Lionfish and Shrimp, Flatworms dancing through the dark waters, grazing Sea Cucumbers, Crayfish, an Octopus hanging out in the nooks and crannies of a coral bommie and a resting Wobbegong Shark.

Climbing back aboard T6 we enjoyed a quick hot shower and headed inside for dinner. The buffet meal included thick pumpkin soup, coconut chicken curry with rice, lasagna, sesame noodles, garden salad and bread rolls with butter.

Dinner complete, divers headed back to the rear deck to prepare for the second dive of the evening: the pace really picked up when the dive crew announced that the coral was spawning, right now!

Second Dive 10.08pm – Saxon Reef – Coral Gardens – CORAL SPAWNING. Looking down into the water, we could already see thousands of pink eggs floating on the surface. Jumping in, it was like entering a glass of champagne. Visibility was reduced and in the torchlight, thousands of pink coral eggs massed through the warm, dark waters. Being in the middle of coral spawning is sometimes described as being in an underwater snowstorm and now I can understand that reference. Descending down through the eggs, we followed their trail to the beds of staghorn corals. Resting gently, we watched the eggs as they were released. It was amazing, memorable and magical. Just to be there, witnessing the world’s largest, living tropical reef system reproduce: what a privilege. Divers moved across the site, witnessing staghorn and mushroom corals spawning. Some divers come back year after year for coral spawning: those who had been before said this was the most prolific event they had seen in many years.

Dive complete, we climbed back on board and took a hot shower. The Tusa Dive crew efficiently prepared the boat for departure and by 11.15pm, we were motoring back to Cairns. The trip passed quickly with a few cold beers and T6 moored at Marlin Marina at around 1am, guests dispersing into the night.

Thanks to Stuart Ireland for the use of his 2011 Coral Spawning pictures. Stuart was with us on Tusa Dive that night and these are his pictures, taken that night.