As you head out from the shores of east Bali on your morning dive you are surrounded by a host of tiny outrigger fishing boats, their sails flashing in the sunlight as they dance over the waves. It is a unique, entrancing and inspiring sight, all the more so because this is a very special place.
These fishermen (and you in your dive boat) are scudding over waters that lie on the cusp of geological and biological change. In the past, at times of low sea levels, this coastline marked the very tip of a massive Eurasian Continent. During those periods you could have walked all the way from Bali to Paris without getting your feet wet. However, even when the world’s oceans were at their lowest ebb, you could never have gone any further east without harnessing wind or mechanical power, due to the depth of the chasm between Bali and Lombok, the next island in the chain.
In the 19th century the great naturalist Alfred Russel Wallace spent time in the islands of what is now Indonesia and remarked on how different the species of bird and animal living in the west of the archipelago were from those that inhabited the east. His findings led him to draw a line on a chart that ran through the Makassar Straits between Borneo and Sulawesi, crossed the Banda Sea and continued down through the straits between Bali and Lombok. To the west of the line, in Bali, Borneo and beyond, animal and bird life was predominantly Asian. On the other side of the line, in Lombok, Sulawesi and further east, the animals and birds were strikingly different, mainly species that originated in or resembled those found in New Guinea or Australia. Brilliantly, he deduced that the reason was geological rather than biological: “I believe the western part to be a separated portion of continental Asia, the eastern the fragmentary prolongation of a former Pacific continent.” Of course, we now know that he was absolutely right!
During his trip Wallace also came up with the notion that natural selection was the driving force behind evolution. At the same time Charles Darwin was on the Beagle sailing the seas on the other side of the Pacific and drawing similar conclusions. But that is an entirely different story.
A Very, Very Big River
What Wallace could not know, in fact something that no-one noted until almost 100 years later, was that one of the factors preventing species crossing Wallace’s Line was an enormous moving body of water. The fossil and historical records show that elephants, orang-utans, bears, tigers and other Asian mammals never managed to bridge the gap. They got as far as Borneo and Bali but no further. Even those animals that tried to swim over or were caught on driftwood after a flood could never make the crossing as everything that enters the water on one side of the line is swept away far from land long before it can reach the other side.
In the Pacific Ocean to the northeast of the Indonesian archipelago, the sea level is about 20 centimetres above average. In the Indian Ocean south of Indonesia the sea level is 10 centimetres below average. This 30-centimetre drop between the oceans creates water movement on a massive scale, a phenomenon variously known as the Indonesian Throughflow or Pacific – Indian Throughflow. The most direct path between the oceans and the path taken by a large portion of the Throughflow, as you may have guessed, runs right along the Wallace Line between Borneo and Sulawesi then down through the straits between Bali and Lombok.
Visualise it as a very, very big river pouring through a canyon between continents. How big? Ocean current flows are measured in units called Sverdrups with one Sverdrup being 1 million cubic metres of water per second moving past a given point. The flow of the Amazon is about half a Sverdrup and the combined flow of all the rivers in the world is about one Sverdrup. The flow of the section of the Indonesian Throughflow that courses past the eastern tip of Bali is estimated to be 2.6 Sverdrups, that is, two and a half times the total of all the rivers of the world put together!
Creatures Great and Small
Thus, a vast amount of water is drawn from the Pacific Ocean and sweeps through tropical seas, across the equator and past the islands of northern Indonesia. As it travels, it picks up and carries along with it an enormous quantity of marine larvae, eggs and juveniles and deposits them wherever it encounters land. It is no surprise that most of the legendary Indonesian scuba diving destinations lie along the route taken by the Throughflow. For example, the calm bays of black volcanic sand in northeast Bali are astonishingly rich in rare species. Enterprising dive operators need only sink a stripped motor bike frame or a dozen broken bottles set in a block of concrete and they soon become a collecting point for small fry seeking sanctuary. These tiny fish attract predators such as frogfish, lionfish, scorpion fish, eels and other rare and fascinating creatures and they in turn attract scuba divers and snorkelers.
Dive guides who work in the area often report larger sightings too, such as dugongs and a host of cetaceans, including killer whales. There are sightings of bizarre and highly unusual marine life. Last year an amateur diver captured video of a long entirely transparent eel; the film became a Youtube sensation.
Diving the Throughflow
Beyond the calm water in the bays, the Throughflow provides dramatic drift diving along unusual seascapes. Towering barrel sponges lean at 45 degrees as if in the presence of a powerful wind and, in places, pinnacles and walls are scoured of their usual natural coating. But in the valleys and other places where the topography provides a little shelter from the onslaught of the current, the enormous profusion of corals and fish life can take your breath away. In one bay, for example, just a few metres off shore from the lines of colourful fishing boats that decorate the beach, you can find hectares upon hectares of multi-coloured staghorn coral, as glorious a sight as any of Bali’s rice field terraces. Drifting over these fields of pointed sculpture in pastel shades, populated by clouds of damselfish which rise and fall as you pass is a true magic carpet ride.
Cool Animals in Cool Water
The Throughflow passes by the southeast coast of Bali too and close to the village of Candidasa a series of small islands, some not much more than jagged shards, are home to some of Bali’s fishiest diving. Schools of jacks, rainbow runners and barracuda use the dramatic rock formations for shelter from the current and reef sharks circle around watching for weakness and waiting to strike.
Further south, attempting to block the southern end of the Lombok Straits like an ill-fitting plug is Nusa Penida, the exposed part of an undersea ridge that connects Bali with Lombok. The Throughflow races by on both sides of this island, offering healthy coral, lots of big animal sightings and exhilarating drifts. Sometimes, however, the ride can be a little too wild and conditions can change rapidly and vary dramatically. One day you will drop in on a site and be entertained by a dozen manta rays, which sweep in from the deep to feed on plankton in calm, bottle green water. On another day, the same site will be empty of fish and the ocean will merely throw you around in a soup of spume and spit you out into the southern ocean on a fast train ride to the horizon.
Seasons have an effect on the speed of the Throughflow, with August usually the strongest month when the southeast monsoon is at its zenith. This also coincides with mola-mola season around Nusa Penida. The arrival of these bizarre creatures may be linked to the increased strength of the current but this time of year also sees an upwelling of colder water in the south of the Lombok Straits and that may be significant too. The reliability of mola-mola sightings during this period has created a small boom in the local diving industry. Be warned if you are thinking of joining the crowds: water temperatures can drop to the high teens centigrade but when you are face to face with an oceanic sunfish measuring four metres from tip to tail you will probably not even notice!
Diving into the World’s Fastest Tidal Rapids
In the mystical waters just north of Vancouver, Canada lies a narrow channel called the Skookumchuck Narrows, or simply “The Skook.” It’s a hidden gem in the Salish Sea that boasts a unique spectacle – a tumultuous dance of tides and currents that draws adventurers and spectators from far and wide.
Imagine this: a channel so narrow and shallow that a single tide can unleash an astonishing 200 billion gallons of water, creating a tumultuous display of standing waves, whirlpools, and currents surging at 16 knots (18 mph or 30 kph). Such speeds may seem mild when driving a car, but the erratic water is a different ballgame. Skookumchuck Narrows is a contender for the title of the world’s fastest tidal rapids, rivaled only by Nakwakto Rapids further up the British Columbia coast.
But there’s a twist – this aquatic battleground isn’t just for adrenaline seekers; The Skook is an oasis for life beneath the waves. April 2023 marked a rare convergence of perfect conditions: a celestial alignment allowing divers to witness The Skook in all its glory. And who better to guide this daring expedition than Porpoise Bay Charters, a family-run venture led by the seasoned Kal Helyar and Ann Beardsell?
Raging currents = an abundance of life
The allure lies not in the danger but in the vibrant marine ecosystem fueled by the relentless currents. Ocean currents act as nature’s turbochargers, transporting nutrients that transform places like Skookumchuck Narrows into underwater havens with colorful life thriving amidst the rocky terrain.
It’s important to debunk the myth that this is a reckless plunge into chaos. Diving The Skook is not about courting danger but choosing the right moment: at slack when the tide turns, the water experiences minimal movement, and the currents are a mere 4-5 knots. Picture this – a scuba diver slipping gracefully between tidal changes, maneuvering with precision as the water changes its course and gradually picks up speed. Timing is everything, and finding the rare dates when daylight piercing through the emerald-green water coincides with navigable water conditions is critical. April 2023 granted us a mere handful of these golden days of nature’s alignment for the first time in four years.
Entering the abyss
As our vessel, under the watchful eye of Captain Kal, approached the infamous Skookumchuck rapids, a tangible excitement filled the air. These cold-water adrenaline-filled dives are the scuba diving equivalent to scaling Everest. The unpredictability of The Skook, where currents can whisk you in any direction, demanded respectful caution from our experienced salty crew.
With a reassuring smile, Captain Kal dismissed the notion of a toilet bowl experience, where divers are pulled in a circular direction by the currents as if flushed down a toilet. He emphasized that they only dived during an easy drift in the current, which was hard to fathom possible in such treacherous waters. Approaching the narrowest section of the channel, where the current was fastest, Kal’s experienced eyes scanned for the telltale signs of slack tide. Tidal ripples slowed, and we entered the water in the few precious minutes within the next year when it was possible to witness Skookumchuck in all its sunny glory.
As we descended into the underwater world, a mysterious algal bloom cast a dark green haze, unveiling a breathtaking palette of colors below. Bright red and pink anemones, neon orange encrusting sponges, and deep purple ochre sea stars adorned the rocky canvas, showcasing nature’s artistic prowess.
Surrendering to the sea
Descending further, we felt the force of the tide, like a river yet to subside. Gripping onto rock holds and kicking into the current, we felt like underwater rock climbers. Adjusting our underwater camera settings and getting comfortable with the flow of the water, we marveled at the transformation of the underwater landscape. Slabs of rock, once pounded by the current, now hosted a vibrant community of marine life.
After a mesmerizing twenty minutes of relatively gentle water, the current intensified, signaling the roller coaster drop ahead. We surrendered to neutrality, letting the current guide us along the wall. Boulders and back eddies added a touch of unpredictability; with trust in our abilities and Captain Kal’s promise of a safe pickup, the thrill was exhilarating rather than menacing.
As the current ebbed, we found ourselves in a tranquil cove adorned with green sea urchins, marking the end of our underwater odyssey. The Skook had shown us its splendor: a delicate balance of chaos and life beneath the surface – leaving us with memories as vivid as the colors we witnessed.
About the Author
Nirupam Nigam is a dedicated underwater photographer and fisheries scientist. While growing up in Los Angeles, he fell in love with the ocean and pursued underwater photography in the local Channel Islands. He received degrees in Aquatic and Fisheries Science and General Biology, as well as a minor in Arctic Studies, at the University of Washington. After working as a fisheries observer on boats in the Bering Sea and North Pacific, Nirupam became the Editor-in-Chief of the Underwater Photography Guide and the President of Bluewater Photo – the world’s top underwater photo & video retailer. Check out more of his photography at www.photosfromthesea.com!
US-based divers: explore more close-by dive destinations with Bluewater Dive Travel here.
All photos: Nirupam Nigam
Unveiling Indonesia’s Dive Gem: Welcome to Bunaken Oasis, Where Adventure Meets Luxury
Embark on a journey to a sanctuary meticulously crafted with a single vision: to redefine luxury diving in North Sulawesi. Born from a culmination of global experiences, our resort stands as a beacon, promising an impeccable fusion of opulence and ecological mindfulness.
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As your boat docks at our private jetty, the journey begins through the elegant Long House, leading to an ethereal infinity pool overlooking the horizon. Beyond lies our haven: a cocktail bar, a panoramic restaurant serving culinary excellence, and a serene spa to soothe your soul after underwater escapades in the awe-inspiring depths of Bunaken Marine Park.
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Bunaken Oasis stands as a beacon of ethical tourism, securing recognition for our commitment to nature. With an extensive infrastructure ensuring minimal environmental impact, we’re pioneers in nurturing and enhancing the marine park’s wonders.
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Explore an aquatic wonderland at Bunaken Oasis, offering access to 80 diverse and stunning dive sites. Encounter majestic sea turtles, some so colossal they seem prehistoric, gracefully navigating vibrant reefs.
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Join us at Bunaken Oasis Dive Resort & Spa, where luxury meets responsibility, and every moment resonates with the harmony of nature.
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