How a Massive "Blue Hole" In the Great Barrier Reef Went Unnoticed for So Long

There’s a big blue hole in the Great Barrier Reef, and Johnny Gaskell won’t tell you where it is. The Australia-based diver and videographer says he found the unique formation on the internet before checking it out in meatspace.

“After spotting this blue hole on Google maps, we decided to head far offshore, further than our normal reef trips to see what dwelled within,” Gaskell told The Cairns Post. “What we found inside was hard to believe considering five months ago a Category 4 cyclone went straight over the top of it.” Down inside the blue hole, which he estimates is 50 to 65 feet deep, Gaskell says he found remarkable coral growths.

“There were huge Birds nest Corals (Seriatopora) and super elongated Staghorn Corals (Acropora), both of which were among the biggest and most delicate colonies I’ve ever seen,” Gaskell told The Cairns Post. It makes sense that corals inside the formation are thriving, given that the deep water in a blue hole is often way cooler than in the surrounding ocean.

But wait, you may be wondering, What the heck is a blue hole?

A blue hole is basically a sinkhole or cavern in the ocean. It’s a geological phenomenon that occurs when carbonate bedrock — composed of limestone — erodes and collapses below the level of surrounding rock. Most blue holes formed as caverns during the last ice age and filled with water and coral as the oceans rose.

Because the water in the hole is so much deeper than the surrounding water, it looks like a much deeper blue. Hence the descriptive — if a bit uncreative — name.

Gaskell’s Instagram post history suggests that his typical diving range includes the sections of the Great Barrier Reef off the Whitsunday Islands about halfway down the coast of Queensland, Australia. These include Bait Reef and Hook Reef, which are relatively close to Queensland compared to other parts of the Great Barrier Reef.

It’s not that surprising that the blue hole hadn’t been discovered yet, since scientists are still discovering new coral reefs to this day.

Given the fact that sections of the Great Barrier Reef are under distress maybe it’s okay that Gaskell doesn’t want to share the location of this spot. And since it sounds like it’s pretty far off the coast, it’s probably not on anybody’s usual route. But for anyone who lives in the area and is up for the adventure, perhaps he’ll tell you.

If you liked this article, check out this video of 3D-printed synthetic coral reefs.