See inside the Great Barrier Reef’s incredible blue hole for the first time

As Aussies we are lucky enough to have some of the world’s most beautiful landscapes in the world right on our doorstep, but there is still some beauty we don’t know about.

The Great Barrier Reef is full of the promise of something new and mysterious, and after finding a blue hole on Google Maps, Australian marine biologist Johnny Gaskell decided to have a closer look.

Blue holes have perhaps the most straightforward of names for a geological formation, but for marine researchers the watery sinkholes hold treasure troves of information and are anything but straightforward.

“Due to the sediment build-up over thousands of years, blue holes can be like time capsules for the ocean,” Gaskell said.

“Within the walls of the blue hole it is perfectly still, no current at all. What stands out is the large coral colonies that have grown into interesting shaped formations, likely due to the lack of current and disturbance from wave action. These colonies form abstract structures that seem to have no pattern, growing outwards and changing course at random.”

At its centre, this particular blue hole is just shy of 30 metres deep. An abundance of marine life such as turtles and tropical fish inhabit the waters.

According to Gaskill, the coral growths extend only a portion of the way down. Once they had descended to the blue hole’s dark bottom, they discovered that it was mostly sandy sediment.

Yesterday in the Great Barrier Reef!!! After spotting this deep blue hole on google maps we decided to head far offshore, out further than our normal Reef trips to see what dwelled within. What we found inside was hard to believe considering 5 months ago a Cat 4 cyclone went straight over the top of it. At around 15m – 20m deep there was huge Birdsnest Corals (Seriatopora) and super elongated Staghorn Corals (Acropora) both of which were among the biggest and most delicate colonies I've ever seen. Totally unaffected by the cyclone. The position of this deep hole within the lagoon walls has obviously protected these corals for decades. We may very well be some of the first to dive this deep hole as it was hidden within one of the Great Barrier Reef's biggest lagoons…

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Yesterday's Blue Hole mission in the Great Barrier Reef. This Blue Hole has previously been explored and documented by geologists who suggested it could be even older than the famous Great Blue Hole, in Belize. It's location is in one of the least explored parts Great Barrier Reef, over 200km from our home @daydreamislandresort . To get there we had to travel overnight for 10 hours and time the tides perfectly… Was well worth it! Inside the walls was similar to the site we explored a few weeks back, but this hole was deeper and almost perfectly circular. We dived down to just over 20m yesterday, before hitting bare sediment, that slowly sloped towards the centre. Again it was great to see big healthy coral colonies. Stay tuned for video footage of the coral within…

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Gaskell began searching for blue holes in March last year after Cyclone Debbie hit, in hope of finding coral that was spared from the storm.

The high walls that line the sinkholes tend to preserve what lies below from damaging weather. Large hurricanes can be particularly dangerous for corals, as they are smashed by swells.

The blue hole that Gaskell spotted on Google Maps was in a remote location, nearly 190 kilometres away from the nearest island. While the specific blue hole had been previously identified, its remoteness made it difficult to access and little was known about it. Gaskell was able to finally confirm that it was a blue hole during the diving expedition in September.

The majority of blue holes are formed from sinkholes or caves that develop slowly over time, as rock begins to erode and collapse. Many of the world’s blue holes formed during the last Ice Age, after sea levels rose and filled existing sinkholes with water.

The term blue hole simply comes from the dark, navy waters that characterise the formations, often creating a striking contrast with the turquoise that surrounds them.

Gaskell plans to continue looking for and surveying blue holes in the Great Barrier Reef.

“Some of these sites have had scientists explore them in the past, but due to the remote offshore location, there are still parts of the Great Barrier Reef that remain a mystery,” he said.

After going on his expedition a few months ago, Gaskell has finally released the amazing footage of inside the hole to National Geographic, which you can view above.

Via National Geographic