Cocos Islands


Splendid Isolation

By Beth and Shaun Tierney

Cocos Islands

Flying in to the Cocos (Keeling) Islands, you could be forgiven for thinking that you were about to land somewhere else. The scenery has that familiar Indian Ocean look: the lagoon is a bright turquoise, the islands are spits of pale yellow and covered with a deep green shroud of coconut trees.

As the Captain banks into the runway, you see the golf course beneath you. That’s because the golf course and the runway are much the same thing. Twice around makes 18 holes. The siren has sounded and the golfers decamped. The plane lands and you disembark by the first tee. It’s then that you realise that this is not your usual island paradise, but one that’s somewhat quirkier.

Cocos Islands

Cocos is part of Australia. The bigger continent owns these tiny islands technically, but not emotionally. The horseshoe shaped atoll is one of those nationless sort of places that has kept quietly to itself for decades, except perhaps as a staging post. In the two world wars, Direction Island was a telecommunications station. The Germans did try to attack once, unsuccessfully, and since then Cocos has returned to a quite haven of localised Malays and peace-seeking ex-pat Aussies.

The real reason to come to this isolated outpost is water sports. There’s surfing and windsurfing and diving – with a sub- aqua reputation for big stuff. Being in the middle of nowhere, the atoll attracts pelagics who feed on smaller species that inhabit the reefs. We headed across from our base on West Island to

Cocos Islands

Direction Island, opposite. It only took 20 minutes before we were introduced to a lagoon dive that was surprisingly barren. Affectionately known as ‘diving the desert’ the seabed was sculpted by currents and tidal surges. We dropped to a smooth rocky surface that was peppered with hard coral outcrops.

The marine life was strangely prolific with groups of yellow snapper, rainbow runners, anthias and pyramid butterflies swarming around. There were whitetip sharks resting on a sandy slope. We finned quietly past them and across to two raised ridges where we watched a manta fade into the blue and then, swimming back towards the boat, came across three cannons dumped onto the sea floor. No one knows their history but they sit close to the coralencrusted, WWII telecommunications cables that stretch across the seabed.

After a picnic lunch on Direction’s perfect white beach, we dived just a short distance from our first site and discovered a great little wreck. Sitting upright on the sand, were the remains of a fibreglass refugee boat. The engines and some of the structure are still intact, but the hull is slowly disintegrating. Underneath, sweetlips and rabbitfish sheltered from the grey reef sharks that zipped past.

Cocos Islands

The underwater scenery changes dramatically once you head outside the lagoon. The atoll’s outer walls are densely coated in hard corals. Lane Cove was smothered in growth interspersed with some sandy shelves. Beds of garden eels poked up from the sand. From our vantage point behind them, we could see several barracuda hanging off the wall. We moved off and they followed, staying nearby for the entire dive. Up on the top of the reef there were schooling trevally interspersed with clouds of pyramid butterflyfish, one of the most prolific species on the reefs here.

Cocos Islands

Cologne Gardens, just off the edge of Horsborough Island, is so lush you couldn’t find a blank space to put a finger down even if you’d wanted to. We dropped to the base of the wall to see Karen’s favourite peach coloured fans and had only been there moments when we heard her squawking through her regulator. Wondering what the problem was, we looked up to see her laughing so hard her mask was flooding. Behind us were two young whitetip sharks. They’d been sniffing our fins – literally – when one of us had given a solid kick and frightened them off.

Cocos Islands

After exploring as much of the atolls as we had time to do, we finally came to our last day and the choice to revisit our favourite dives. It was a hard call but we decided to revisit the small refugee wreck. Karen, who is an eagle-eyed spotter, took us from a huge green moray to a tiny pink pipefish, thought to be unique to the islands. We met a pair of giant triggerfish and realised they were mating, performing an elegant rotating dance around each other. Over our shoulders a blacktip shark was also taking an interest and within moments we saw some whitetips and a grey. We headed back to the wreck and found all our fishy friends from a few days ago still sheltering.

We were heading home when we met a pod of bottlenose dolphins. The skipper chucked us into the water, then took the boat off to play with them, spinning it – and the dolphins – around us. What can you say but there is nothing in the world like looking a truly wild dolphin in the eye and having him smile right back.

It’s all too easy to get to an idyllic Indian Ocean getaway these days. But going off the beaten track can reap all sorts of rewards. A return to a style of diving where you join in every aspect of your dive day from launching the boat to setting up the picnic. There’s only one dive centre on Cocos so only ever one boat. Just imagine that? There’s only one restaurant too, one pub, one shop. There’s no entertainment except beachcombing at sunset and playing with the hermit crabs. What more could you want?

Cocos Islands

Swimming through cobalt blue-white passageways with vision limited only by the power of our dive lights, the expanse of tunnel disappears ahead into a liquid infinity. The railway tunnels of Australia’s longest water-filled cave have become legend amongst cave divers both at home and overseas. We have come to see them for ourselves. Not just to look along the kilometres of submerged limestone, but to attempt a journey to the known end of the cave and just possibly…beyond.

Over a year ago I was lurking on one of Australia’s online diving forums. The subject was ‘Cocos Islands’, the best known of the thousands of Western Australia’s famous Nullarbor Plain caves. A cynical diver made a throw-away comment to the effect of ‘any cashed up diver with a rebreather and some scooters could get to the end of Cocos Islands these days!’ The words struck a chord with me because I had been thinking of trying something exactly along those lines! But was it really as easy as the armchair expert on the internet had suggested? Divers I had spoken to recently with Cocos Islands experience had made me believe it was anything but simple…no matter what techno-toys you took along for the ride. Mountainous rock-piles, achingly long swims and extraordinary isolation were all factors not to be taken lightly.

Cocos Islands

So what started as a vague idea had to be firmed up into a concrete plan. I needed to talk with someone who had real life experience in the cave. For that I turned to Craig Challen, a Perth cave diver and one of only a handful of divers who had been to the end of the main passage in the site’s third sump. In 2003 Craig supported Karl Hall in a quest to extend the end of the known cave. After scootering the 1.6km first section of the cave to the ‘Rock Pile’, they carried gear over the chamber to the second sump. Next they commenced the 2.5km underwater traverse to the second massive dry chamber known as ‘Toad Hall’. Finally, with the assistance of two other divers they entered the third and final 1.6km sump and began to swim.

Cocos Islands

Near the end of the main line in the third sump, they stopped at a restriction where the French divers had started their final push in 1983. At this point Karl removed his rebreather then pushed on with open circuit equipment, while Craig waited patiently for his return. During the 52 minutes that Karl was gone, Craig’s rebreather began to malfunction and he endured a nerve wracking wait. Karl didn’t have it much easier with some buoyancy and gas problems meaning that whilst he made it to the end of the permanent line (laid by Australian Chris Brown in 1995), he couldn’t go any further. Twenty-nine hours after entering the cave, the team exited in a state of complete exhaustion and without achieving their primary goal of extending the cave. In other words… Craig had unfinished business in the cave. I offered to support his push to the end of the cave and so our plan was born.

To fully understand the hardships Cocos Islands has to offer, one has to look to the story of the early exploration. After the initial exploration dives in the first sump in 1972, it rapidly became apparent that extending the cave required large scale expeditions with multiple cylinders and support divers. The side bar at the end of the article outlines where important progress has been made in the cave, but the effort and courage needed by the early explorers swimming massive sledges loaded with tanks through the long sumps defies belief! Martyn Farr’s book ‘The Darkness Beckons’ contains a beautiful summary rich with images and makes essential reading.

Back to the present day expedition. Our aim was to take a more lightweight ‘Alpinist’ approach to the cave. Get in and out in the shortest possible time using long range rebreathers and scooters that we could transport across the much feared rock-piles without an army of support divers. Sounds easy eh? Two factors loomed as critical to our success: rebreather duration (in particular the duration of the CO2 scrubber) and scooter battery duration. The traditional use of open circuit scuba requires vast numbers of cylinders to be both staged and breathed in the cave. A single long range closed circuit rebreather could take the place of literally dozens of tanks. Craig and I both owned (modified) units which we felt could perform for 8-10 hours underwater without ‘recharging’. The second problem lay in the scooters. To get the scooter duration required for the cave was usually resolved by using multiple large (heavy) scooters which needed to be disassembled to be transported across the dry chambers. We each wanted to use a single lightweight scooter with extra long duration batteries. The standard battery in our scooter of choice only ran for 60 minutes whilst we needed three hours. How to do it without increasing the weight? We turned to fellow cave diver John Dalla-Zuanna (JDZ) for the answer. He is one of Australia’s most experienced cave divers and he disappeared into his shed with a couple of other boffins for several months! Just days before the trip and with much angst from all parties, JDZ reappeared with the solution in the form of superbly made lithium ion battery packs for the scooters. The final R & D would have to occur in the cave!

The final team of nine divers assembled at the cave from both sides of the country. Ken Smith from Adelaide attended as a diver but more importantly brought his unique radiolocation technology (the ‘Pingers’). These could be used to locate precise points within the cave with GPS and hence add detail to the map of the third sump. Doug Friday and Geoff Paynter from Perth came to document the trip with video and still photography. Mark Brown, John Currie, Simon Doughty, JDZ and I completed the complement of divers to assist Craig’s quest for the end of the line.

Is Cocos Islands hard work? The short answer I was soon to discover was an unqualified YES! Harder than I could have imagined! With every passing day loading gear into the cave, transporting it to the cave lake and then through the first sump and across the Rock Pile to the second sump…it became clear that a strong back and a high pain threshold was required! To my internet friend who believed Cocos Islands to be a ‘doddle’, I was given to frequent cursing! So much for a lightning raid to the end of the cave with minimal assistance. Even with our gas saving rebreathers and lightweight scooters we still needed the assistance of all the divers and several days to get prepared to tackle the second sump.

Only then could Craig and I set off for our first foray into the second sump. 20 minutes into the dive to stage tanks in the 2.5km long sump, Craig’s scooter died. So I pushed on for my first visit to Toad Hall solo, staging some cylinders on route. Toad Hall…300m of enormous boulders and stiflingly humid air to traverse. Not a place I wanted to linger on my own and certainly not somewhere to sprain an ankle or worse. This dive had revealed a problem with our ‘top secret’ scooter batteries; one scooter had gone for 20 minutes whilst the other had performed perfectly for three hours. The boffins all disappeared back into the ‘shed’ and emerged with theories about chargers, resistors and other electronic mumbo jumbo, and over the next few days the scooter batteries started to perform as expected. We were back in business!

With gas staged in the second sump, Ken and Simon took the opportunity to visit Toad Hall and add their names to the slate that resides there (40 names in total now). With the scooters operational, Craig and I did our second dive to Toad and spent several hours transporting gear to the start of the 3rd sump. With a 12 hour turnaround, I was beginning to really sense how exhausting trips into the cave could be.

A rest day and a ‘hamburger with the lot’ at the Cocos Islands Roadhouse, then another day with equipment problems finally saw us in good shape for the push dive. Having good support divers make or break this kind of venture. John and Mark came out to the Rock Pile with us and carried our scooters into the second sump. That just left us to stagger across with our ‘breathers on our backs. A speedy 65 minute scooter to Toad Hall had us in the start of the third sump well ahead of schedule. To avoid carrying more scooters across Toad Hall we had decided to swim the third sump. We activated the Pingers before departure so Ken could follow our progress from the surface. Three of these we deposited at important points in the cave and these were located by Ken from the surface and the GPS points recorded. Sixty minutes into the third sump and the cave had changed substantially. No longer were we in the enormous tunnels of the first and second sumps. Now the cave closed in and became more complex, jagged and interesting. Haloclines split the water like shivering mirrors. Truly one of the most beautiful places I have ever been. At 90 minutes the cave appeared to almost come to a halt and the large yellow cord laid by Hugh Morrison was replaced by fine white line. Here, Craig removed his rebreather and set off through a restriction, breathing from his sidemounted tanks. Hurrying along the line and conscious of his finite gas reserves, Craig Challen swam into the darkness over six kilometres from the cave entrance. I was left alone with my thoughts while he pushed the cave.

At the end of one third of his first cylinder, Craig reached a restriction that he could not pass with both cylinders. Removing the partially depleted cylinder, he pushed the second tank ahead of him through the slot, his body following behind. No ordinary cylinder, this second one carried dual regulators and its own buoyancy device to safely assist his passage. Once through the ‘no-mount’ restriction, Craig reached the end of Chris Brown’s line about 200m from where I waited. And ahead of that…more cave passage awaiting exploration. Without pausing, Craig tied off a new reel and swam on another 120m before it was time to stop as he reached his gas reserves. He glanced ahead at the cave still beckoning him on. Next time perhaps…

The underwater reunion 70 minutes after Craig’s departure was glorious! Great to see him back safely and equally exciting to see his almost empty exploration reel! Turning for home we started the slow exit from the cave. To say Toad Hall was painful on the way home would be an understatement. Twenty hours after entering the cave, we surfaced in the entrance lake to a warm reception, a hot meal and a beckoning sleeping bag.

The following day Simon and Ken returned to Toad Hall to extract the remaining cylinders, and Ken swam far into the 3rd sump to retrieve all but one of the Pingers. Two more days to clear out the cave and Ken and I hit the road for the 16 hour drive back to Adelaide. One last bit of excitement awaited us. On the way home my 4WD caught fire and the vehicle and all our dive gear were completely destroyed by the flames. Yep, Cocos Islands is easy. Anyone with a scooter and a rebreather could do it…

Important Dates in the Exploration of Cocos Islands Cave



First documented dive in cave.


First expedition, pushed 300m into first sump.


End of first sump reached, second sump noted (Allum, Beilby, Morrison et al)


Toad hall discovered, 3rd sump noted (Allum, Morrison and Rogers et al)


French Cave divers’ explore 3rd sump (to 1550m) with scooters and composite cylinders to total distance of 6090m (Le Guen et al)


Australian’s return to push 3rd sump with more streamlined equipment, adding 250m more line to 1790m (Allum, Morrison and Rogers et al).


Chris Brown et al adds 20m in third sump using a unique dual tank off mount system.


Eberhard and Payne ‘Alpinist style’ dive to Toad Hall.


Hall and Challen (et al) visit the end of Brown’s line in the third sump using closed circuit rebreathers.


Challen and Harris (et al) add 120m to third sump using CCRs and lightweight scooters.

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