Dr James Gilmour, a coral ecology expert with the Australian Institute of Marine Science (AIMS), recalls being awe-struck the first time he saw these reefs: “It was the early 2000s. I wasn’t prepared for how big and abundant everything was, the size of the atolls themselves, the populations and varieties of fish, giant clams, sea cucumbers. The diversity of corals. It was, and still is, one of the healthiest reef environments in the world.” These are the Rowley Shoals, and they might be the best dive destination you’ve never heard of.

The shoals lie 260km offshore from Broome / Rubibi, a pearling town on Western Australia’s northwest coast. They were first charted in 1818 by Captain Phillip Parker King of the British Royal Navy. Then aged just 26, King explored and mapped the, at the time difficult to access, Kimberley coast region of Western Australia. He named the three atolls after Captain Rowley who’d visited himself 18 years earlier; King’s vessel was HMS Mermaid, Rowley was commander of HMS Imperieuse, while Clerke Reef was named for a whaling boat captain known to frequent the area. The shoals all appear remarkably similar – tear-drop shaped, each between 10 and 14 kilometres long and six to eight kilometres wide. Clerke Reef sits 23 kilometres south of Mermaid Reef, Imperieuse Reef 35 kilometres south of Clerke.

Dr Gilmour’s research focuses on the northern reefs off Western Australia, specifically, the long-term dynamics of coral communities – how they adapt to the impacts of natural and human-induced stressors. According to James, Rowley Shoals has so far occupied a kind of ‘goldilocks’ zone as we’ve watched our oceans warm: “If you look at a map showing the extreme levels of ocean warming in recent months, Scott Reef, situated 460km northeast of Rowley Shoals, has been hit by the worst of it. But the ocean around Rowley Shoals, far less.”

In recent years, coral bleaching has occurred with alarming frequency, and all over the world. There have been minor bleaching events at Rowley Shoals, but not yet any mass bleaching.

“When the ocean temperature reaches two degrees above the usual range for more than a few weeks, corals will expel the algae from their tissue. Without the algae, the tissue is translucent, and you can see the white calcium-carbonate skeleton, hence the term coral ‘bleaching’. The corals may recover their algae, but if the elevated temperatures persist, they may not. This leads to the sight no diver or snorkeler wants to see, of dead, slime covered reefs, the fish-life long since vanished,” adds James.

The shoals are actually drowned sandstone mountaintops, as opposed to extinct volcanoes, a legacy of much lower sea levels in ages past. It’s supposed that coral larvae were carried here by currents flowing south from Indonesia. “Since the last ice age, growth of some of the coral reefs along the edge of the Continental Shelf managed to keep pace with sea-level rise. Three atoll systems remain at or near the ocean’s surface – Scott Reef, Ashmore Reef, and Rowley Shoals,” says James. Rowley Shoals is the southernmost, inhabited by 230 different types of coral and 700 species of fish.

Like anywhere in northwest Western Australia, protection largely comes down to splendid isolation. To give you some idea, my visit in November of 2023 began with flights from Sydney to Perth / Boorloo to Broome, a hotel overnight stay, and then a late afternoon boat departure and all-night motoring to reach the shoals. You won’t stumble across this special spot. The few hundred visitors here a year are those who are on a mission to explore some of the world’s most untouched and beautiful ocean environments. Given the near-pristine state of Rowley Shoals, government oversight is a serious business. Various government agencies work together on surveillance, reef management and scientific research projects.

In April of 2023, Cyclone Ilsa put Rowley Shoals suddenly onto the world media radar, when it left eleven Indonesian fishermen stranded on Bedwell Islet, a ribbon of sand in the heart of Clerke Reef. The fishermen were spotted from the air and then rescued, after six days, by members of the Australian Maritime Safety Authority. As dive and snorkel boats only visit the area from September until November, the fishermen were on their own in April.

This incident served as an important reminder, if any were needed, that there’s still high demand in Asia for sea snails (trochus niloticus), sea cucumbers and shark fin, all species that have been illegally taken here. “Illegal fishing is a complex issue,” says James. “These are Australian waters and if you don’t have the appropriate permits, you shouldn’t be fishing here. But there are multiple economic factors driving this behaviour – everything from the impacts of Covid, to corporate-driven greed targeting certain marine species, to global pressures brought about by the Ukraine war. My sense is that most fishermen are driven to do what they do by some form of
economic necessity.”

There are in fact fisherfolk on board my boat trip, and while the skipper allows fishing only in those zones where it’s permitted, I can report that we eat what we catch, and leave the echinoderms (sea cucumbers) and mollusks (sea snails) alone. The legal targets out here include wahoo, yellowfin and dogtooth tuna, sailfin, and Spanish mackerel. Trolling with artificial lures, our crew land some impressive Spanish mackerel and yellowfin tuna but report losing half a dozen fish to savvy whaler sharks and tiger sharks.

Most tour boats moor inside Clerke Reef, for its sheltered snorkeling and diving and the sliver of sand that is Bedwell, the only landfall we make on what is otherwise a five-night liveaboard trip. Here, schools of tiny fish coloured electric blue, green, or purple dart among the staghorn coral gardens. Wildly colourful, globally threatened, humphead Maori wrasse (Cheilinus undulatus) and bumphead parrotfish (Bolbometopon muricatum), some a metre long, nibble away at the hard corals. Black-tip reef sharks flit among the sandy shallows, while scuba divers keep a lookout for silver-tip whaler sharks which are broader and altogether more ‘sharky’, as they swish by overhead.

Sea anemones can be just about any colour, but until I snorkel ‘The Aquarium’ (so named for its peppering of shallow fish-festooned coral ‘bommies’), the ones I’ve seen previously were shades of orange, brown and cream. Here, I find myself goggling at one that’s a blazing neon purple.

Equally mind-hurtling are the clownfish protected by its poisonous tentacles – a dozen or so tiny juveniles coloured midnight blue with bands of iridescent aqua. It’s difficult even for marine scientists to say which fish or corals might be endemic to Rowley Shoals, although in my own experience, isolated atolls like these typically have unique variations on some familiar species.

Three parallel channels run into the heart of Clerke Reef, the narrowest of them known to boat skippers as the ‘dinghy channel’, because nothing bigger will fit through. Tides hereabouts can rise or fall by five metres in six hours, among the world’s largest.

Dive masters take advantage of the tides, dropping snorkellers at the entrance to the dinghy channel for a ‘drift’ snorkel. It’s effectively an 800-metre-long amusement park ride, face-down mask-on, over the top of a magnificent aquarium. On a turning tide, we’re able to take a current-free meander along several cracks in a coral wall that lead up to a section of exposed outer-reef flat. Schools of blue-green parrotfish are everywhere, as are Moorish Idols, countless ‘chromis’, and varieties of pufferfish I’ve not seen anywhere else. Later I gear up for a scuba dive, descending to 20 metres and drifting along a coral wall with enormous red and orange sea-fans and plate corals the size of coffee tables. Hovering beneath are pairs of coral trout and banded snapper. When our group of four divers surfaces, we kick away from the wall and float about in the great blue yonder grinning at each other in silent stupefied awe.

I last puttered towards the (now world-famous) Bedwell Islet in 2010, in a boat tender carrying six divers plus food and drink supplies, planning a lazy afternoon on the beach. I wrote then: “Bedwell is used as a rest-stop by red-tailed tropicbirds, white-bellied sea-eagles and ship-bound divers.”

Nothing has changed, and yet everything has changed. Global temperatures look set to sail past the 1.5 degree rise above pre-industrial baselines, nudging human survival into uncertain territory. The attendant sea-level rise, now five millimetres per year, might see this tiny islet, which is two metres above sea-level at its highest point, eventually swallowed by the Indian Ocean.

In April of 2024, Dr Gilmour joined a dozen other scientists to spend three weeks aboard AIMS research vessel RV Solander. Climate models already predict coral bleaching and coral mortality at Ashmore and Scott reefs. Rowley Shoals, however, seems to have been spared. James intended to examine all three to assess coral damage but also resurveyed long-term monitoring sites, took samples for laboratory genetic analysis, and contributed to the development of a framework to guide management decisions, including novel interventions.

The research Dr Gilmour and coral scientists like him are doing is both pragmatic and optimistic. Scientists won’t stop ocean warming any time soon, but managing coral reefs through future warming will benefit from their triage approach: identify first which part of a reef, and which particular types of coral, have escaped the worst of the impacts from climate change; explore farming the corals that are best adapted to ocean warming and other pressures. “Corals are sensitive and fragile, but some prove to be surprisingly resilient too. What we continue to learn about them will inform management practices, and, we hope, ultimately preserve pristine reefs like the Rowley Shoals,” concludes Dr Gilmour.