Underwater encounters – soft coral, skull caves and bioluminescent birdwatching

Skulls caves, waterfalls, bioluminescent birdwatching. Sometimes the most amazing diving is not the most memorable part of an adventure. A trip to Tawali Dive Resort in Papua New Guinea helped me discover one of my favourite dive sites in the world but it was everything else I found there that made this place unforgettable. Let’s dive in one last time.

Getting there

Just getting to Tawali is an adventure. First you fly from PNG’s capital Port Morseby to a remote town in PNG’s south east, called Alotau. From there a rambling mini bus drive takes you past villages and through jungle. You spot farms, villages and plane wrecks nestled in the bush. Two hours later you are unloaded at a small wooden dock. Suitcases are passed through the mini bus window and piled onto a boat. We head out as the last fishermen head in from the day on wooden canoes. A mass of green looms above a wooden jetty as dusk falls. This is Tawali, we’ve made it.

Soft corals and jungle skies

Over the coming days we left our mountainous new home to explore the nearby reefs. Motoring out on the dive boat we’d see flying fish leap out of the water and dart across the surface. One day we came upon a site called Deacon’s Reef. Looking up at the jungle I stepped off the boat and descended. Coral reef greeted me in every direction, colourful and alive with a rainbow of fish. Swimming along I followed our guide, so far nothing unusual here. We weaved between rocks covered in sponges and encrusting coral. I found myself in a gully, a rock wall on one side rose from the sea floor to the surface.

Looking up took my breath away. It wasn’t a wall it was the edge of the land. Above me the sunlight shimmered through the jungle, creating a sparkling green ceiling. The gully grew shallower, I was swimming upwards towards the jungle. Looking away from the land I saw a mass of vibrant colours. Soft corals in the most delicate shades of pink, yellow and orange grew in clumps. I floated at the bottom of the gully. Looking up at the soft corals, fish swam above me like birds among the reflections of the jungle. It was a disorienting, beautiful world.

Soft corals don’t grow calcium carbonate skeletons, they’re not reef builders like hard corals. Every soft coral polyp has eight tentacles instead of six, placing soft corals and sea fans in in a group called Octocorals. Some octocorals have algae in their tissues called zooxanthellae. This algae converts sunlight into food through photosynthesis, similar to terrestrial plants. Other soft corals don’t contain any zooxanthellae. They rely on underwater currents to bring their plankton food to them. These algae-free soft corals are easy to spot as they are bright shades of red, orange, pink and purple.

Surfacing from the dive, the surreal feeling persisted as we went on a shopping trip in the ocean. Local villagers had paddled out in their canoes to sell jewellery and shells. Mitch picked a necklace for me while bobbing beside the canoe.

Waterfalls and skull caves

Back at the resort that afternoon we kept exploring. A local guide, Gilbert, took us to see some caves. It was overcast but muggy in the jungle, the air felt heavy with water. Descending into the first cave we felt the temperature drop. Cool relief! As our eyes adjusted to the darkness, we followed a short path deeper, down into the earth. Rounding a bend, we came upon a strange formation.

White stalactites hung from the cave ceiling. When the torch beam hit them, they sparkled as if covered in glitter. My eyes slid down to a pile of white rocks stacked up at their base. But they weren’t rocks. They were skulls. Piles and piles of human skulls filled the cave. Empty eye sockets stared blankly up at us. Some skulls had begun crystallising and also glittered. It was eerie, but beautiful. A natural tribute to ancestors. Or a hiding place of murdered enemies? Like everything in PNG you can never be quite sure.

Back in the daylight and the heat we ventured on. The sun had begun to go down and the dusk was creeping in. Following a path through the jungle we arrived at a waterfall. The forest was quiet except for the splash of water. A calming end to an action filled day. We were all silent on the boat back to the resort.

Bioluminescent bird watching

For our last day on the island we set our alarms for 3am. We were going bird watching. By 4am we were on a boat heading into the dark sea. Stars twinkled above, fading as the dawn approached. It was pitch black except for a strange light trailing the boat. Water splashing along the boat and in our wake flashed blue, like electric sparks in the black ocean. The neon blue light spread along the sides as we sped up. Bioluminescence.

Many marine organisms can produce light from a chemical reaction within their bodies. This is called bioluminescence. They do this when being attacked, trying to attract a mate or when physically disturbed, such as when a boat makes waves. Lots of animals can produce bioluminescence, including plankton, jellyfish, sea stars, fish and sharks. The one thing these species all contain is a molecule called luciferin that creates light when it reacts with oxygen.

In the predawn light we began scrambling uphill. The muddy path wound up the side of a mountain. Bugs landed on us, the mud sucked at out sandals. Our guide sped ahead, nimble in his thongs, hacking errant branches off the path with his bush knife. We trekked onwards, upwards, the day grew lighter. Finally we stopped in a small clearing at the top. Our guide looked up. We did too, not quite sure what to look for.

Finally, he pointed up. I couldn’t see anything. I stared at the green, hoping a shape would materialise. He pulled me closer and pointed again with his arm next to my head. There it was, a brown, bedraggled shape amongst the leaves. A bird of paradise. It had arrived at its morning roost to sing its mating call. But today it was silent. We all looked up, waiting. But he flew from one tree to another then left in silence to get on with his day. It was an incredible end to our trip. We headed back to the island to pack and say our goodbyes. A week of underwater and topside encounters had left us with a lifetime of memories and a vow to return.

This was the final post in the Underwater Encounters series! I hope you’ve enjoyed reading about some of my favourite marine memories and this has inspired you to get out and make your own. This series was produced as part of an assignment for my Masters in Science Communication. If you have any tips, tricks or other feedback to help me improve my science communication please comment or message me. It’s time for me to abandon ship. Until next time may you have fair winds and calm seas.

Underwater encounters – Octopus gardens and shark stacks

“It was winter and the water was a chilly 14 degrees. I inhaled sharply as it soaked through my wetsuit, 7 millimetres of neoprene doesn’t stop you getting goose bumps. Ignoring the cold, we kept swimming out. There was something offshore we’d come to see and it only happened once a year…”

We have another guest post for this series! Marine biologist and keen macro photographer Mitch joined us to chat about his favourite underwater encounters. Let’s dive in!

Meet Mitch (the one on the left)

Huskisson, N.S.W

Today we’re taking you to Huskisson, a small coastal town on the south coast of NSW. Husky, as the locals call it, sits in the Jervis Bay Marine Park. This makes exploring temperate reefs really accessible if you pop on a tank and swim straight out from the beach. Mitch and his buddy had come to dive a site called Dent Rock.

“Dent rock is a small rocky reef sitting 150 metres offshore from Orion beach. It’s marked by a buoy on the surface because the reef can be only 2-5 metres below the surface depending on the tide. This makes it perfect for diving because boats avoid it. We hauled our gear down a steep set of stairs and walked out through the shallow breakers. Picking our way over rocks we began to swim out, the water was only about three metres deep over the weed banks.”

Swimming out over the seaweed Mitch and his buddy kept an eye out for interesting critters to photograph.

“As you move along you find patches in the weed, surrounded by shells. Empty shells from clams, scallops, mussels, pipis, every kind of mollusc that usually buries itself in the sand were piled up in circular clumps. In the centre of the shell piles was a hole that seemed to drop down to nowhere, but if you’re lucky it drops down to an orange, brown and cream speckled octopus.”

Mitch points out one of two octopi/octopuses (whichever you prefer). Can you spot the other one?

Octopus Gardens

These strange homes are called octopus gardens (we know you just started humming the Beatles song). A lot of creatures like the taste of octopus so to avoid being eaten they hide in dens. The octopus camouflages its home by building gardens of shells and rocks around it, some even have a rock ‘door’ they pull over the opening to seal themselves safely inside.

An octopus in its garden of shells

“It’s clear these creatures are full of personality. Some can’t keep their eyes off you, they pop as far out of their hole as they can when you approach. If you float down to the weed bank they float higher to keep an eye on you. Others want absolutely nothing to do with you and sink deep into their holes, pulling shells over their heads for cover.”

Close up of an octopus

“All that and we hadn’t even hit the reef yet! Jervis Bay is a pretty special spot because it serves as a breeding aggregation site for Port Jackson sharks. Breeding aggregation, that doesn’t sound particularly special but you end up with hundreds of sharks piling on top of each other, all with no concept of personal space.”

Port Jackson Sharks

Each year between winter to early spring, Port Jackson sharks migrate to shallow reefs to mate. Here they congregate in small groups, in caves, under overhangs, and in gutters along the rocky bottom.

“So what psychopath is getting in the water with hundreds of sharks? Well that’s the other bonus, Port Jackson’s or PJ’s as we call them, are the puppy dogs of the ocean. These bottom feeders eat sea urchins, crabs and molluscs (invertebrates with shells), anything they can root out of the sandy bottom. They’re really not interested in you unless you give them a hard time.”

“PJ’s for anyone that hasn’t seen one, don’t look like your stereotypical shark. They’re a square headed fish reaching a maximum length of 1.65 metres. Their skin is brown with black lines that make it look like they’re wearing a harness. They have rounded fins with small spines just in front of their dorsal fins. Even their teeth are unusual. They have flattened plates perfect for crushing and grinding up their food, very different to the pointed teeth you normally associate with sharks.”

A Port Jackson shark up close, note its unusual teeth

The divers had finally arrived at Dent Rock. But could they find the sharks?

“It wasn’t hard, they were scattered everywhere over the bottom. Heads and tails were going in every direction, no one was fussed that they were being lain on or were laying on someone else. The great thing is these sharks just don’t care. We spent a lot of the dive just hovering above the sand watching them, face to face. They watch you back. There are honestly few encounters with sharks where you can feel this comfortable.”

Stacks on! Three Port Jackson sharks lay in a gap in the reef

It never ceases to amaze me what you can find by simply swimming off the beach and having a look around. Mitch had researched the timing of the shark aggregation but didn’t expect to see the octopus gardens. He can’t wait to explore more underwater in his own backyard once it’s possible to travel again.

Images are a mix of my own photographs and those provided by Mitch.

Underwater encounters – Can you make friends with fish?

To some people, fish seem completely devoid of personality. You’ve seen one fish you’ve seen them all. In my experience this hasn’t been true. A few years ago, I volunteered at the research station on Lizard Island. This island is a picturesque tropical paradise, named for the goannas traipsing around the beaches. The island is also home to a resort and the Australian Museum’s research station. Coral reefs surround the island and are used as an underwater lab by researchers and students.

A turtle and its hangers on

One morning before my volunteer work began for the day I snuck down to the beach for a snorkel. Heading offshore I passed beds of seagrass growing out of the sand. Then I came across a green sea turtle having breakfast. This herbivore was feeding on seagrass, which turns the fat in its body green – hence its name.

I watched the turtle as it swam and grazed. There was something weird about this one. Finally, the turtle swam up to take a breath and I could see two large fish firmly attached to the bottom of its shell.

These fish were remoras, more commonly called suckerfish. Their name means delay or hinder, which is an accurate description. Their dorsal (top) fin has evolved into a flat plate on the top of their heads. This suction disc contains collagen fibres to maximise the remoras contact with its host. Collagen comes from the Greek word for glue. You might be familiar with collagen because it is the most abundant protein in your body and gives your skin that plump look. The suction disc also contains thousands of tiny spines that increase friction, helping the fish ‘stick’. This allows remoras to suction themselves onto larger, moving animals. The bond is so strong a remora can stay attached to a dolphin even when it leaps out of the water!

So, what was the remora doing on the turtle? Well it depends on the species. Some remoras just opportunistically feed on their host’s food scraps and get a free ride. They spend little energy when another animal transports them so don’t have to eat much. Other remora species help their host by removing parasites. When both animals benefit this relationship is called commensalism. So, it seems fish can get along with other sea creatures.

Remoras can also have commensal relationships with people. In some parts of the world remoras are used in fishing. How you ask? Well a fisherman attaches a line to a remora, sends it off into the ocean and the remora attaches itself to a turtle or larger fish. The fisherman can then carefully reel in the remora and the animal it is stuck to. The fisherman catches something and the remora is fed scraps for its job.

Snorkel side kicks

I had a hanger on myself once. One afternoon during an internship in Exmouth, Western Australia I went for an afternoon snorkel. My boyfriend and his parents were visiting so I took them to the nearby Bundegi Boat ramp to see what was living underneath. We saw the usual stonefish sitting grumpily in its PVC pipe, the schools of baitfish and the occasional angelfish that had drifted in from the nearby Ningaloo Reef.

A little yellow fish decided to swim with us for most of our snorkel. It was about the size of my pinky, yellow with a few black vertical stripes. It looked a little cartoonish thanks to its large eyes that looked up at me. It would swim along with me for a while, hiding in my shadow then if I duck dived it would abandon me for my partner nearby. Back and forth it swam between us, happily joining our snorkel.

This fish was a juvenile golden trevally. Juveniles of this species often form groups and follow larger fish like groupers, sharks and even SCUBA divers. They do this because the large fish protects them from being eaten by other predators. The large fish doesn’t eat the juvenile trevally because they are fast moving and can out manoeuvre their host.

It is clear to me that individual fish have personalities and science is starting to back this up. In one study of guppies individual fish reacted differently to stressful situations indicating different personality types. Research continues with another study about to begin which examines how much butterfly fish personality varies between individuals living on different reefs. But can fish be your friend? Well this little yellow fish found something to like about us and tolerated the rest. Not that different from any human friend really. These encounters taught me that whenever you get in the water there’s a chance to interact with marine life. Make sure these are positive for all involved.

Underwater encounters – dancing sharks and moody fish

For the second post in this series I interviewed a special guest. Let me introduce Paul Baskys, a dive instructor who lived and dived in Papua New Guinea for three years. I sat down with Paul and asked about his most memorable underwater encounters. Here’s what he told me…

Titan Triggerfish

Paul’s first story takes us to the Pai 2, a wreck dive south east of Port Moresby, PNG. This old Japanese fishing boat was purposely sunk in 1982 to form an artificial reef dive site. It’s a great dive, you slowly swim around the boat, which is bursting with life. Schools of glassfish smother the wreck. Colourful sponges and soft corals decorate the rusted steel hull.

While Paul was exploring Pai 2 his dive buddy swam up to him and began gesturing. In strange underwater sign language his buddy, Mitch, pointed at the stern then crossed his arms in a big X shape. Paul nodded, don’t go near the stern, got it! He looked over but couldn’t see what Mitch was so worried about and continued exploring the wreck.

Everyone was running low on air so it was time to head back to the boat. Paul swum back over the wreck, past the stern, heading towards the reef where the boat was waiting. Something caught his eye. A titan triggerfish! These large fish have a sharp beak for crunching through coral and sea urchins. Their eyes are enormous and independently rotate to follow your every move. They’re one of Paul’s favourite species and he hadn’t seen them on the Pai 2 before.

The triggerfish looked like it was feeding. Its snout nudged around in the algae growing on the wreck. Paul swam closer to shoot some video. The fish tensed its body like an athlete at the start of a 100 metre sprint. It turned away, then suddenly spun and swam straight at Paul. He quickly retreated. The triggerfish snapped at the camera, spun around, and lunged at the camera again. Satisfied the human was far enough away the triggerfish went back to its business.

Paul finally understood what Mitch was warning him about. Mitch had seen the nest of triggerfish eggs, a pink gelatinous mass, early in the dive. Both male and female triggerfish will aggressively defend their nests. On a dive a few months later Paul saw a nesting triggerfish under a boat mooring. Having learnt his lesson, he was able to steer a group of divers away from a similar attack.

Grey Reef Shark

The second story also took place in PNG when Paul was leading a dive off Fishermen’s Island (aka Daugo Island in the local language). The dive is on a coral wall near the edge of the continental shelf, where the ocean floor drops down to 600 metres. Divers jump in and drift along the wall, meeting the boat at a rendezvous point.

Looking away from the wall Paul spotted a shark. It was an adult grey reef shark, about two metres long. Normally sharks propel themselves forward using their tail (caudal fin) which makes their head slowly wiggle from left to right. This shark’s movements were exaggerated. It was bending its head almost 90 degrees to each side. Paul looked back at the divers obliviously staring at the wall and decided to keep an eye on shark that was still about 40 metres away.

The divers continued to drift along the wall. The shark arched its back and dropped its front (pectoral) fins. Paul decided it was time to move the divers on. He got the group’s attention and signalled it was time to head to the rendezvous point. One diver got excited, waving at everyone, and pointing behind Paul. All nine divers swam past Paul straight towards the shark. This was bad as dive leader it would be his fault if something happened, but also good because there were now nine other people between him and the shark.

The shark continued its threat display and swam closer. It was now 15 metres away. Paul herded the group back towards the boat. Out of the water everyone was excited about the shark encounter. One diver remarked, “Wasn’t that an awesome dance the shark was doing?!”. Paul dived the site again over the coming months and saw many grey reef sharks but luckily none were ‘dancing’.

Paul’s stories highlight the incredible natural behaviours we can witness up close underwater. These stories also serve as a warning to learn a little about the creatures you may encounter so you know what they’re really trying to tell you.

To read more about shark threat displays check out R. Aiden Martin’s article https://www.tandfonline.com/doi/full/10.1080/10236240601154872

Underwater encounters – shallow water secrets

I’d like to share a little secret. One of my favourite encounters occurred in water that didn’t even reach my knees. Let me explain. I was on holiday last year at Lissenung Island, a speck of paradise to the north of mainland Papua New Guinea. Every day we’d hop on a boat and head to dive sites, speeding through mangrove lined shallows to get to coral walls that dropped off into deep water. Now don’t get me wrong, these sites were amazing. Fish swarm the walls in constant, colourful motion. Turning around you’re faced with an expanse of deep blue ocean. Also alive, with schools of large silver trevally that shimmer past. Occasionally a turtle lazily flapped by. Hanging in mid water staring into the abyss you could watch a reef shark curiously circle above divers staring obliviously at the coral wall.

Between dives at sites like this the crew would take us to sheltered spots for the dive interval. This gives us an hour topside to let the nitrogen levels in our blood drop so we could stay down longer on the next dive. On one of these breaks the boys took us to a sandbar. I munched on fresh coconut and soaked up the tropical sun while staring absently at the green mangroves. Someone brought me back to reality saying, “I think there’s a clownfish next to the boat”. The dive snacks were forgotten. We donned our masks and slipped over the side to float in the shallows. The ocean was as warm as bath water, like those shallow rockpools you come across that have been soaking in all the sun’s heat. Beneath the surface seagrasses waved lazily. Small coral patches and anemones littered the sand.

In every crevice there was something alive, a crab darted into a crack in the coral. Small yellow fish schooled amongst the seagrass. But the clownfish were amazing. In such shallow water we saw three different types. My favourite was the Clown Anemonefish (Amphiprion percula). It was my first time seeing these cuties, shaped like a typical Disney Nemo but with more black colouring. A cool thing about these clownfish, the amount of black pigmentation changes depending on which species of anemone they live with. You see, anemones are happy to host lots of different anemonefish species. Clown Anemonefish are picky, they’re only happy to call three anemone species home. If a Clown Anemonefish doesn’t find a magnificent, gigantic or leathery sea anemone to live in it will perish quickly. This relationship is called a symbiosis. The fish are protected from predators by the anemone’s stinging tentacles (like living in a jellyfish). In return the fish bring snacks to bed, dropping food offerings into their anemone host in return for this safe haven.

“Come look at this!” Robert, one of the crew called us into even shallower water. He pointed at a brownish blob well camouflaged in the sand. “Devil scorpionfish, very dangerous, don’t step on him” Robert warned. We all peered at the scraggily brown blob that blended perfectly with its sandy surroundings. This ambush predator waits for a meal to come to it. While seemingly lazy, they speedily lunge and inhale smaller fish when they swim too close. When feeling threatened Devil Scorpionfish (Scorpaenopsis diabolus) lifts the venomous spines along their back, revealing why it is one of the world’s most venomous fish. If you step on a scorpionfish you can be in severe pain for up to 12 hours. Luckily it can be treated with hot water, which can be found even in the most remote locations. Naturally my dive buddy and macro enthusiast boyfriend, Mitch, had to get a shot. We all laughed at him lying in the shallows.

With so much to see the dive interval was over before we knew it. The dive crew grinned as we suggested we do the next dive at the sand bar. A little reluctantly we all hopped back on the boat to go to the next ‘real’ dive site. With so much to see in shallow water, I’d learnt to check out any puddle, rockpool or barely flowing river I came across from then on. Let me be the first to tell you, you don’t need much water to have a cool aquatic encounter!