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Trip report: 25th April – 3rd May 2026 - Mergui Archipelago & Burma Banks

19/5/2026

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Sunset over Black Rock in the Mergui Archipelago, Myanmar, during a Smiling Seahorse liveaboard diving trip.
Some trips end quietly. Others feel like the ocean emptying one last treasure chest before the season closes.
Our final expedition of the 2025–2026 season carried us once again from Ranong into the wild islands of the Mergui Archipelago and out toward the remote Burma Banks. Calm seas, glowing sunsets and reefs overflowing with life accompanied us through a week where every dive seemed to reveal something different: hunting pelagics, curious macro life, frogfish, sharks, pipefish and endless nudibranch encounters hidden among the corals. It felt like the Andaman Sea had decided to offer one final encore before the monsoon silence returned.​

Day 1 – From Ranong to the Mergui Archipelago
​

After clearing Thai immigration in Ranong and Burmese formalities in Kawthaung, we sailed north into the maze of islands forming the Mergui Archipelago. Jungle-covered silhouettes slowly replaced the mainland while guests settled into the rhythm of liveaboard life, preparing cameras and comparing fish books before the first dives of the trip.
Vibrant orange sunset over the Andaman Sea horizon during a liveaboard diving trip to South Twin and North Twin islands, Myanmar.
One of many spectacular sunsets in the Mergui Archipelago.

Day 2 – South Twin, Boulder Rock & North Twin

​Our first dive at South Twin Rock Head offered an easy and colourful introduction to the archipelago. Longnose emperors cruised over the reef together with schools of rainbow runners, yellowback fusiliers and neon fusiliers. Along the walls, macro life was already everywhere: spotted Hypselodoris, Chromodoris geometrica, Chromodoris annulata, creamy chromodoris, twin chromodoris, Indian Caloria and bicolour flabellina covered the reef while peacock mantis shrimps watched cautiously from their burrows. McCosker’s flasher wrasses darted above the rubble slopes while powder-blue surgeonfish and moon wrasse moved constantly through the current.
Macro photography of a Girdled Glossodoris nudibranch on a reef at Boulder Rock, Myanmar.
The intricate patterns of a Girdled Glossodoris spotted at Boulder Rock.
A group of colorful Wrasse swimming over a vibrant coral reef in the Mergui Archipelago.
Vibrant reef fish dart among the corals during our final expedition of the season.
At Boulder Rock, the scenery shifted into dramatic boulders and darker overhangs filled with life. A devil scorpionfish rested motionless between sponges while porcelain crabs and peacock-tail anemone shrimps decorated the cracks. Schools of fusiliers streamed above the reef while giant trevallies occasionally passed through the blue. Chromodoris geometrica and Indian Caloria continued the nudibranch parade across the rocks.
A well-camouflaged Devil Scorpionfish resting among sponges and rocks in Myanmar's Andaman Sea.
Can you spot the Devil Scorpionfish blending perfectly into the dramatic overhangs at Boulder Rock?
A large school of yellow fusiliers streaming over rocky reef formations at a Myanmar dive site.
Schools of fusiliers provide constant motion above the dramatic boulders of the Mergui Archipelago.
​North Twin Reef delivered both schooling fish and pelagic surprises. Batfish hovered calmly in formation while schools of fusiliers and surgeonfish drifted above the reef. An eagle ray appeared suddenly out of the blue together with African pompano cruising past the divers. Clown triggerfish, mullet fish and juvenile blackspotted sea cucumbers added life to the shallows, while ornate sapsucking slugs, blue dragons, spotted Hypselodoris and Chromodoris annulata covered the reef in colour.
Vibrant pink soft coral surrounded by a large school of yellow snapper on a rocky reef in North Twin Bay, Mergui Archipelago.
The reefs of North Twin Bay come alive with vibrant soft corals and swarming schools of fish during our Myanmar liveaboard adventure.
A group of four scuba divers giving okay and peace signs while underwater in the clear blue waters of the Andaman Sea with The Smiling Seahorse.
Our guests enjoying the final dives of the 2025–2026 season in the pristine Mergui Archipelago.
​The night dive in North Twin Bay brought an entirely different atmosphere. Blunt decorator crabs, pygmy squid, squat lobsters, juvenile lobsters and several squids emerged after dark. Harlequin shrimps hid beneath rubble while octopus hunted across the sand beside batfish and filefish sleeping in the reef. A red abalone glowed under torchlight while flatworms and Jebb flatworms drifted slowly across the substrate.

Day 3 – Black Rock
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We spent the full day diving Black Rock, and the site once again reminded us why it remains one of Burma’s most legendary offshore pinnacles. Schools of bigeye jacks and round batfish circled endlessly around the rock while great barracuda, African pompano and Spanish mackerel patrolled the blue water. Dogtooth tuna occasionally appeared in the distance while yellowback fusiliers and lunar fusiliers formed dense silver rivers around the reef.
A wide shot of Black Rock in the middle of the blue Andaman Sea during a Myanmar liveaboard cruise.
Approaching the remote and wild dive sites of the Mergui Archipelago, like Black Rock, where isolated rocky islands hide incredible underwater treasures.
: A large school of silver Bigeye Trevally (Jackfish) swimming through deep blue water at a dive site in Myanmar.
Underwater action: A massive school of trevallies passes through the blue, a common and thrilling sight for divers in the Mergui Archipelago.
Closer to the rocks, the macro life was just as spectacular. Orange-spotted pipefish and network pipefish hovered carefully between soft corals while juvenile oriental sweetlips danced along the walls. Peacock mantis shrimps, peacock-tail anemone shrimps, marbled shrimps and tapestry shrimps carrying eggs filled the cracks. A yellow warty frogfish remained perfectly camouflaged among the sponges while white devil scorpionfish rested motionless nearby.
Close-up macro photography of a Marbled Shrimp (Saron marmoratus) perched on orange coral during a dive in the Mergui Archipelago.
The intricate details of a Saron Shrimp, one of the many fascinating crustaceans found among the corals of the Andaman Sea.
A well-camouflaged yellow frogfish nestled among pink soft corals and sea stars as a scuba diver swims in the background at a Mergui Archipelago dive site.
Can you spot the master of camouflage? A bright yellow frogfish hides in plain sight among the vibrant soft corals during our final Myanmar expedition.
​The nudibranch diversity was extraordinary: Chromodoris geometrica, Chromodoris annulata, Chromodoris reticulata, Bornella anguilla, bicolour flabellina and Dendrodoris lumpy appeared throughout the dives. Juvenile yellow boxfish drifted shyly around the reef while tiger cowries covered the walls.
One unforgettable moment came when a large female octopus was seen digging a nest to prepare for egg laying, carefully moving sand and rubble while guarding her future nursery. Nearby, another pair of octopuses were observed mating among the rocks.
Macro shot of a Bornella anguilla nudibranch crawling on a hydroid at a Myanmar dive site.
Adding to our nudibranch count: The unique Bornella anguilla was just one of the extraordinary species spotted during our dives.
A large octopus camouflaged against the rocks and coral in the Mergui Archipelago, Myanmar.
An unforgettable encounter: We observed an octopus carefully preparing a nest, a rare and beautiful moment of natural behavior in the wild.
As the sun dropped lower, Black Rock transformed once more. Boxer shrimps carrying eggs, straight-face swimming crabs and squat shrimps became increasingly active while schools of batfish and jacks continued circling the pinnacle into dusk.
The silhouette of the famous Black Rock dive site at sunset, a premier remote diving destination in the Mergui Archipelago, Myanmar.
A golden farewell to Black Rock: Watching the sun set over Myanmar’s most legendary dive site during our final liveaboard expedition of the season.

Day 4 – Shark Cave, Square Rock & Submarine
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​At Shark Cave, tomato clownfish defended their anemones while anemone crabs and squat shrimps filled the reef crevices. A dead banded sea krait rested inside the cave entrance, creating an unusual and slightly eerie sight. Siboga cuthona, Hypselodoris, spotted Hypselodoris, Chromodoris annulata and Hypselodoris bollandi decorated the reef while blue dragons drifted delicately across the substrate. A large fimbriated moray eel peered from the shadows beneath schools of fusiliers and snapper.
Macro photo of a colorful nudibranch with purple and orange markings on a reef in the Mergui Archipelago.
A splash of neon: This specimen was one of many vibrant nudibranchs discovered during our dives at Square Rock.
two tiny white porcelain crabs camouflaged on a bright green plate coral surrounded by black damselfish at the Square Rock dive site, Myanmar.
A hidden gem at Square Rock: These delicate porcelain crabs find a perfect home on a vibrant green plate coral.
Square Rock revealed one of the highlights of the day: a rare white seahorse perfectly camouflaged among soft corals. Nearby, Glossodoris cincta guarded its eggs while boxer shrimps carrying eggs hid beneath ledges. Spotted Hypselodoris, Dendronotus sp.2 and a Persian carpet flatworm added even more colour to the reef. One curious reminder of the region’s past appeared underwater as unexploded dynamite still resting on the seafloor.
Square Rock revealed one of the highlights of the day: a rare white seahorse perfectly camouflaged among soft corals. Nearby, Glossodoris cincta guarded its eggs while boxer shrimps carrying eggs hid beneath ledges. Spotted Hypselodoris, Dendronotus sp.2 and a Persian carpet flatworm added even more colour to the reef. One curious reminder of the region’s past appeared underwater as unexploded dynamite still resting on the seafloor.

​
Submarine was bursting with fish life. Schools of yellow snapper, fusiliers, white tongue jacks, golden jacks and trevallies filled the water column while cuttlefish were observed kissing and changing colours dramatically. Orange-spotted pipefish, rust-spotted crabs, red hairy crabs and anemone crabs hid among the coral formations while the reef pulsed with movement from every direction.

​In the  afternoon, we stepped ashore for a visit to the small island temple near Shark Cave, climbing the familiar path through the jungle to enjoy the peaceful atmosphere and panoramic views over the surrounding islands before returning on board for the night dive.
A rare white and brown seahorse perfectly camouflaged against red soft corals at Square Rock, Myanmar.
A tiny seahorse expertly found hiding among the soft corals of Square Rock.
Macro photography of an Orange-spotted Pipefish (Corythoichthys ocellatus) camouflaged against pink coralline algae during a night dive at Shark Cave, Myanmar.
A master of camouflage: This orange-spotted pipefish was a fantastic find during our final macro-focused night dive at Shark Cave.
A Porcelain Anemone Crab (Neopetrolisthes maculatus) peeking out from the tentacles of its host anemone in the Andaman Sea.
A shy resident: A porcelain crab seeks shelter within the stinging tentacles of an anemone during our final night dive of the season.
The night dive back at Shark Cave delivered another excellent macro session. Bornella anguilla and Siboga cuthona appeared again while hermit crabs, anemone hermit crabs and Baba’s crinoid squat lobsters covered the reef. Barracuda hunted in the torch beams while tiger cowries, Ramos murex, curly Chicoreus, rose branch murex and Tapesian horse conchs crawled slowly across the rocks. A fimbriated moray eel hunted openly while Mordilla brocki and Hypselodoris bollandi completed another spectacular night dive.
A silhouette of a rugged rocky island in the Mergui Archipelago, Myanmar, at sunset with the sun reflecting on the Andaman Sea.
Golden hour in the Mergui Archipelago: The dramatic islands of Southern Myanmar provide a stunning backdrop for our final days at sea.
A traditional golden Burmese pagoda and temple building situated on a lush green hill overlooking the Mergui Archipelago.
Beyond the waves: Exploring the cultural beauty and scenic landscapes of the remote islands in Southern Myanmar.

Day 5 – Burma Banks & Blackwater
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The crossing toward the Burma Banks brought calmer seas and wide-open blue water. At Rainbow Bank, nurse sharks rested beneath coral formations while schools of surgeonfish moved continuously across the reef. Roe Bank delivered more shark encounters together with turtles, schools of jacks and large groups of bignose unicornfish, sleek unicornfish and bluespine unicornfish cruising over the sandy plateaus. Honeycomb moray eels hid beneath the bommies while clown triggerfish patrolled the edges of the reef.
A Honeycomb Moray Eel tucked under a colorful coral head during a sunset dive in the Mergui Archipelago.
A Honeycomb Moray Eel peeks out from the reef as day turns to dusk in the Andaman Sea.
A large school of unicornfish swimming over a sandy seabed in the clear blue waters of Myanmar.
Underwater traffic: An impressive school of unicornfish passing by during our final sunset dive of the season.
During the sunset dive, red-spotted guard crabs carrying eggs hid inside coral heads while the last light filtered through massive schools of fusiliers and jacks.

That night, several divers entered the darkness for a blackwater dive. Moray eel larvae, larval anemones, mantis shrimp larvae, siphonophores, squid and driftfish drifted slowly beneath the boat, revealing the strange pelagic world that rises toward the surface after dark.
A juvenile fish seeking shelter under a small translucent jellyfish against a pitch-black background during a blackwater dive.
The strange pelagic world: A juvenile fish hitches a ride on a jellyfish, a classic symbiotic behavior seen during blackwater diving in Myanmar.
A slender, silver larval fish with a long, pointed rostrum drifting in the open ocean during a blackwater dive.
The incredible forms of the deep: This larval billfish is a rare and exciting find during our blackwater expeditions in Myanmar.
A tiny, translucent larval cephalopod with long arms and visible internal organs drifting in the open ocean at night.
Alien encounters: A delicate larval cephalopod captured during our deep-sea blackwater expedition in the Mergui Archipelago.
A translucent, gelatinous eel floating against a black background in the open ocean.
Living glass: A delicate eel caught in the torch beam during a night spent exploring the pelagic zone.

Day 6 – Roe, Coral & Silvertip Bank

Roe Bank continued to produce nurse shark encounters before we moved toward Coral Bank for two dives filled with life. Hawksbill turtles cruised over the reef while honeycomb moray eels rested beneath coral overhangs. Halgerda tessalata and Maldivian sponge snails appeared repeatedly along the reef walls while schools of fusiliers, unicornfish and surgeonfish filled the water column.
A nurse shark resting on the sandy bottom of the reef surrounded by a school of small fish at Roe Bank, Mergui Archipelago.
One of our many nurse shark encounters at Roe Bank—these beautiful residents are a highlight of our dives in the Andaman Sea.
A massive, colorful coral structure covered in orange and pink growth against a bright blue Andaman Sea background.
The reefs of Coral Bank are filled with life, boasting some of the most vibrant coral formations in the region.
At Silvertip Bank during the sunset dive, grey reef sharks appeared cruising through the fading light together with more nurse sharks resting on the sandy bottom. Honeycomb moray eels remained a constant presence while Maldivian sponge snails crawled slowly across the reef. 
A nurse shark resting peacefully under a large table coral ledge in the Mergui Archipelago.
Finding shelter: A nurse shark takes a nap beneath a massive coral overhang during our expedition through the Banks.
Three scuba divers swimming over a giant, multi-layered hard coral mound on a sandy bottom in Myanmar.
Scale and wonder: Divers explore an enormous coral colony, a testament to the healthy reef systems found in the remote Andaman Sea.
Throughout the day, dolphins could occasionally be heard underwater while diving, their whistles and clicks echoing faintly through the blue water around the Banks.
A dolphin breaking the surface of the blue ocean water in the Mergui Archipelago.
Surface sightings: After hearing their whistles and clicks underwater all day, we were treated to a brief visit by dolphins at the surface.
A circular fisheye lens perspective of a beautiful, spiraling hard coral formation surrounded by a vibrant reef.
A different perspective: The architectural beauty of the Banks' coral reefs captured through a fisheye lens.

Day 7 – Sea Fan Forest & Western Rocky

Sea Fan Forest offered calmer conditions but stunning scenery. Large sea fans and soft corals framed red reef lobsters, stonefish and schools of jacks moving through the reef. Rainbow runners, Spanish mackerel and barracuda hunted above the bommies while mating octopuses entertained divers among the rocks. Queen Isabel cowries, thick-edge cowries, juvenile yellow boxfish and bicolour flabellina added colour to the reef while squat shrimps hid inside the sea fans.
A well-camouflaged scorpionfish resting on a rocky reef between vibrant pink and orange soft corals in the Mergui Archipelago.
Hidden in plain sight: A scorpionfish blends perfectly into the colorful backdrop of soft corals during one of our final dives of the season.
A massive school of fusiliers swimming through bright blue water toward the surface in the Andaman Sea, Myanmar.
Surrounded by life: A thick wall of fusiliers creates a mesmerizing silver curtain as we explore the remote reefs of Southern Myanmar.
At Western Rocky’s Eagle Rock, white tongue jacks and yellowfin barracuda hunted through clouds of jellyfish while rainbow runners swept repeatedly through the current.
The Cave night dive revealed another explosion of nocturnal life. Soft coral cowries, sieve cowries, rigid egg cowries and spindle cowries covered the walls while decorator crabs, elbow crabs, marbled shrimps and tapestry shrimps emerged after dark. Skeleton shrimps clung to hydroids beside Chromodoris reticulata and Mordilla brocki while giant moray eels hunted openly through the cave entrance.
A dense school of shimmering glassfish swirling inside a dark underwater cavern in the Mergui Archipelago
Light in the dark: Thousands of glassfish illuminate the entrance of a sea cave during our morning dive.
Macro photograph of a marbled shrimp (Saron marmoratus) with intricate patterns camouflaged among orange sea fans.
Macro magic: The incredible detail of a Saron shrimp hidden within the reef's vibrant fan corals.
Back on board that evening, we also celebrated Franck’s birthday together, adding another warm and memorable moment to an already unforgettable expedition.
A custom blue and green frosted birthday cake with the Smiling Seahorse logo, celebrated on a liveaboard boat.
Celebrating in style: Back on board, we toasted to Franck’s birthday, making an already unforgettable expedition even more special.
A wide-angle view of a flourishing reef covered in purple and white sea anemones under a bright blue Myanmar sky.
A carpet of life: Exploring the stunning "anemone gardens" that characterize some of the most healthy dive sites in the Andaman Sea.

Day 8 – Western Rocky & BBQ Night

​We dedicated the full day to the iconic reefs of Western Rocky, exploring the different moods of the site from morning light to sunset. Around the Islets, schools of yellowback fusiliers, neon fusiliers and lunar fusiliers streamed over the reef while rainbow runners, giant trevallies and white tongue jacks patrolled the blue. Harlequin shrimps hid carefully beneath rubble, while bluestriped pipefish, cuttlefish, octopuses, blue dragons, Maldivian sponge snails and Chromodoris annulata kept photographers busy between clouds of anthias and surgeonfish. McCosker’s flasher wrasses darted above the reef as porcupinefish and titan triggerfish hovered near the rocks.
A vibrant male Filamented Flasher Wrasse (Paracheilinus filamentosus) displaying bright yellow, red, and blue colors over a rocky reef.
A flash of brilliance: This male Filamented Flasher Wrasse put on quite a show, darting over the reef with its spectacular colors on full display.
A Pharaoh Cuttlefish (Sepia pharaonis) with intricate skin patterns hovering near a dark rocky crevice in the Mergui Archipelago.
Masters of disguise: We encountered this Pharaoh Cuttlefish showing off its remarkable ability to blend into the shadows of the Cave.
Inside the famous Cave, the atmosphere shifted completely. Giant moray eels watched from dark crevices while anker whip coral shrimps, sponge crabs, skeleton shrimps, marbled shrimps and tapestry shrimps covered the walls and sea fans. Bornella anguilla, creamy chromodoris, Chromodoris geometrica, rigid dermatobranchus and Glossodoris cincta with eggs added layers of colour to the dive. Outside the cave entrance, juvenile oriental sweetlips and juvenile emperor angelfish sheltered among the boulders while schools of dogtooth tuna moved through the blue water beyond the reef.
A pair of colorful Harlequin Shrimps (Hymenocera picta) with blue and cream patterns resting on a rocky reef at Eagle Rock, Myanmar.
Double trouble: Finding a pair of Harlequin Shrimps is always a highlight, especially in the vibrant macro environment of Eagle Rock.
A tiny, translucent Whip Coral Shrimp (Pontonides ankeri) perfectly camouflaged among the polyps of a sea whip against a black background.
Master of disguise: A delicate whip coral shrimp hides in plain sight during our exploration of the Mergui Archipelago's deep reefs.
At Eagle Rock, the current brought even more action. Spanish mackerel and dogtooth tuna hunted above dense schools of fusiliers while barracudas cruised along the drop-off. Porcelain crabs, mantis shrimps, bicolour flabellina and Maldivian sponge snails covered the reef, and one unforgettable moment came as sergeant majors aggressively chased a moon wrasse away from their eggs.
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The final sunset dive around the Cave and surrounding reef delivered a perfect closing atmosphere for the day. Slipper lobsters emerged from cracks while octopuses moved across the reef under fading light. Cadlinella ornatissima, soft coral cowries, spindle cowries, sieve cowries and Mordilla brocki appeared one after another as giant moray eels hunted through the darkness. Above us, schools of dogtooth tuna and Spanish mackerel continued their patrols as the last light disappeared over the Andaman Sea.
A close-up of a Tiger Cowrie (Cypraea tigris) with its dark, patterned mantle fully extended, covering its shell while resting on a reef.
A rare look: The intricate, spiked mantle of a Tiger Cowrie completely transformed its appearance during one of our evening sessions.
A bright red Emperor Shrimp (Periclimenes imperator) camouflaged against the red and white surface of a granulated sea star.
Perfect symbiosis: A vibrant Emperor Shrimp hitches a ride on a sea star, a classic macro find in the Mergui Archipelago.
​Back on board, the evening turned festive with our traditional BBQ night on the upper deck. Under a calm sky filled with stars, everyone gathered to share food, stories and favourite memories from the trip while music drifted across the boat. What started as a relaxed dinner slowly transformed into a lively party, with guests and crew dancing together late into the evening somewhere between the reefs of Western Rocky and the open waters of the Andaman Sea.
A diverse group of happy scuba divers cheering with drinks during a BBQ night on the deck of The Smiling Seahorse liveaboard.
To an unforgettable season! Our guests celebrate the final night of the expedition with a traditional BBQ and a toast under the stars.
Two scuba divers, one with a professional camera rig, hovering over a vibrant reef covered in pink soft corals in the Mergui Archipelago.
Capturing the colors of Myanmar: Divers explore the lush soft coral gardens that make the Andaman Sea a world-class photography destination.

Day 9 – Dendro’s Peak & Return to Ranong
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​Our final dive of the trip took place at Dendro’s Peak, a colourful reef alive with both schooling fish and macro treasures. Schools of fusiliers swirled around the pinnacle together with rainbow runners, giant trevallies and barracudas while cuttlefish hovered calmly above the reef. Hidden among the corals were tiger cowries, mole cowries and several beautiful bicolour flabellina, while surgeonfish, wrasses and butterflyfish covered the reef in constant movement.
A tiny, highly camouflaged Allied Cowrie (Ovulidae) matching the color and texture of its host orange sea fan.
Invisible to the untrained eye: This Cowrie is a perfect example of the incredible mimicry found on the reefs of Myanmar.
A long, slender Trumpetfish (Aulostomus chinensis) hovering vertically among bright orange gorgonian sea fans to blend in.
A master of stealth: We spotted this Trumpetfish using the vibrant sea fans at the Banks to hide while waiting for its next meal.
After surfacing for the last time, the Smiling Seahorse began the journey back toward Kawthaung and Ranong. Equipment was slowly rinsed and packed away while guests exchanged photos, favourite moments and stories from the week. From the reefs of the Mergui Archipelago to the shark-filled Burma Banks and the caves of Western Rocky, the trip once again reminded us how wild and diverse these waters remain.

Another season closed, another chapter written in the currents of the Andaman Sea… until the next departure.
A dramatic and colorful sunset over the Andaman Sea with layers of orange, yellow, and deep purple clouds.
The perfect ending to a spectacular season: A breathtaking sunset over the Mergui Archipelago on our final evening at sea.
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The Paper Nautilus (Argonaut): The Ocean’s Most Fragile Cephalopod

12/5/2026

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Paper Nautilus Argonaut Blackwater diving  andaman sea Thailand Myanmar Scuba Diving Liveaboard Cruisea

All about the Paper Nautilus

Paper Nautilus Argonaut Blackwater diving  andaman sea Thailand Myanmar Scuba Diving Liveaboard Cruisea
Female Paper Nautilus have this distinctive shell on this back
Female Paper Nautilus drifting during blackwater dive
Argonauts can be found itching a ride on passing salp during blackwater dive
We first encountered this incredible little creature while Blackwater diving in 2017. At the time, we had absolutely no idea what we were looking at. ​
The first Argonaut we encountered was apparently a female, as male are 10 times smaller (rarely passing the size of 2cm) and dont have a shell.

Since then, we’ve been lucky enough to spot Paper Nautiluses many more times — including during blackwater dives in the Similan Islands — and finally managed to capture a few decent photos.
After some research, we discovered this strange and beautiful animal is called a Paper Nautilus, also known as an Argonaut.
Despite the name, the Paper Nautilus is not actually related to the true nautilus. It belongs to the octopus family and is one of the ocean’s rarest pelagic cephalopods

What is a paper Nautilus?

The Paper Nautilus (Argonauta argo) is a species of open-ocean octopus found in tropical and subtropical waters around the world, including the Andaman Sea, Thailand, Myanmar, and the Similan Islands.

The delicate white “shell” carried by females is not a true shell like a nautilus shell. Instead, it is a thin egg case secreted by the female using two specially adapted arms.
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The female uses this paper-thin structure to:
  • Protect her eggs
  • Control buoyancy
  • Shelter herself in open water

Male Argonaut are tiny — often less than 2 cm long — and do not produce a shell at all.

​One of the Weirdest Mating Systems in the Ocean

Argonaut octopus carrying egg case in the Andaman Sea
Female Paper Nautilus riding a Jellyfish
Argonaut reproduction is famously bizarre.
One of the male’s specialized arms acts as a reproductive organ called a hectocotylus. During mating, this arm detaches from the male’s body and remains inside the female to fertilize her eggs. The female then secretes the papery shell with the tips of two tentacles. She lays her eggs inside the paper shell and watch them until they are ready to hatch and her job is done.
For many years, scientists thought these detached arms were actually parasitic worms because nobody had ever seen a complete male Argonaut.

Nature is weird sometimes.

​The Paper Nautilus and Its Incredible “BCD”

One of the most fascinating things about the female Paper Nautilus is its ability to control buoyancy.
Argonauts are the only known octopuses capable of trapping air from the ocean surface inside their shell-like egg case.
The female swims to the surface, captures a small air bubble, seals the opening using her arms, then descends back into deeper water.
This trapped air acts almost like a diver’s BCD (buoyancy control device), helping the Argonaut achieve neutral buoyancy and drift effortlessly through the open ocean.
​It’s one of the most unique buoyancy adaptations in the marine world.
Paper Nautilus strange buoyancy technics
Paper Nautilus Swimming

5 Amazing Facts About the Paper Nautilus​

Picture
This pelagic octopus uses jet propulsion to escape faster
🐙 1. The “shell” isn’t a shell at all!
Female paper nautiluses don’t actually have shells; they build a delicate paper-thin case just to store their eggs. It’s basically the ocean’s most elegant Tupperware.

🐙 2. The male is so tiny he looks like he forgot to evolve.
Females can grow up to 20 times larger than males. A male paper nautilus is hard to tell from other octopus you see on blackwater dives.

🐙3. They can “glide” underwater using jet propulsion .Like other octopuses, Paper Nautiluses swim using jet propulsion, expelling water through a siphon to move surprisingly fast through open water. Females may also use their delicate egg case to stabilize themselves while drifting in ocean currents.
🐙 4. Paper nautiluses ae true pelagic hitchiners
They grab floating objects—seaweed, jellyfish, even trash—to ride ocean currents and save energy. They’re the backpackers of the sea, but with much better fashion sense.

🐙 5. They can transform into tiny air-sailors.
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By trapping air inside their paper-thin case, females can float at the surface like miniature balloons, rising and falling like they’re on a tiny ocean elevator.
black water diving with a male paper nautilus
Male argonauts can be hard to differentiate from other octopus
Paper Nautilus Argonaut andaman sea Thailand
Male Paper Nautilus are much smaller and do not carry a shell

Where Can You See a Paper Nautilus?

Paper Nautiluses are rarely seen during normal scuba dives because they live in the open ocean.

The best chance of encountering one is during:
  • Blackwater diving (Pelagic night dives)
  • Night dives on remote offshore locations close to deep waters
  • in tropical waters
Rare cephalopods on blackwater dive hiding in salp
They are pelagic hitchhikers, often found riding on salp chains like in this photo

​Why Divers Love the Paper Nautilus

For underwater photographers and blackwater divers, finding an Argonaut is a bucket list encounter.
They are incredibly delicate, rarely seen, and completely alien-looking.
Watching one drift through the water while carrying its paper-thin egg case feels more like encountering a creature from another planet than a marine animal.
pretty portrait of a pelagic octopus in Myanmar waters
Argonautidae photographed in the andaman sea
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