Trip report | Marine Biology cruise with Whale Shark specialist | 20th – 27th March 2026

Marine Biology Expedition from North to South Andaman with a Whale Shark Specialist

Rinda Mony smiling while wearing scuba diving equipment on board the liveaboard. — Meet the expert: Rinda “Mony,” the “Whaleshark Guru” from the Thailand Whale Shark Project, who joined our March 2026 cruise to share her deep knowledge of these majestic ocean giants.

A wide shot of a vibrant orange sun setting over the dark blue horizon of the Andaman Sea, with soft purple and gold clouds above. — Golden horizon: A breathtaking sunset at sea provides a moment of reflection between our underwater adventures in Thailand’s national parks.

Some expeditions are defined by what you see. Others by what you come to understand.

We departed from Ranong, welcoming our international group of guests from Italy, France, the UK and the US, and set course for a marine biology expedition with a Whale Shark specialist, Mony, to learn more about the biggest fish in the seas!

While the ocean chose not to reveal them this time, the experience took on a different depth. Throughout the week, Rinda, also known as Mony, from the Thailand Whale Shark Project, delivered daily presentations exploring whale shark biology, behaviour, and conservation challenges in Thailand.

These sessions brought a meaningful layer to the expedition, connecting each dive to a broader ecological perspective — linking what we observed underwater to the larger story of marine life in the Andaman Sea. From North to South Andaman, the journey unfolded as a rich exploration of pelagic encounters, vibrant reefs, and intricate macro life — shaped as much by discovery as by understanding.

Day 2 – Surin National Park & Richelieu Rock

Our check dive in the Surin Islands at Koh Chi offered a gentle but vibrant start. Garden eels swayed over sandy patches while Halgerda tesselata, blue dragon and scorpionfish blended into the reef. Coral groupers hovered near bommies alongside Clark’s anemonefish and false anemonefish, while schools of yellowback fusiliers and neon fusiliers moved through the water column. Around them, Moorish idols, copperband butterflyfish, blue-barred parrotfish and bullethead parrotfish completed the reef scene.

Macro life was already hinting at what was to come — a richness that would only intensify as the expedition progressed.

A school of Raccoon Butterflyfish Chaetodon lunula showcasing their distinctive yellow and black mask patterns. — A striking group of Copperband Butterflyfish navigates the coral reef with precision. | Frederique Bechet

A white Halgerda tesselata nudibranch with orange ridges crawling over a bright red sponge. — The intricate orange-and-white patterns of this Halgerda Bacalusia nudibranch stand out against a vivid red sponge. | Renaud Liberge

A dense school of predatory fish gathering around Richelieu Rock in the Andaman Sea. — Predatory patrol: Massive schools of fish congregate at Richelieu Rock, creating one of the most dynamic underwater scenes in the world.

Two Moorish Idols Zanclus cornutus swimming through a dramatic rock archway, silhouetted against the bright surface sun. — Into the light: Moorish Idols navigate the dramatic topography and sunbeams of the Surin Islands’ reef systems.

At Richelieu Rock, visibility was excellent and the site delivered immediately. The gang — giant trevallies, bluefin trevallies, bigeye trevallies, longnose emperors and rainbow runners — hunted through dense clouds of glassfish. Barracudas patrolled the edges while batfish hovered calmly mid-water.

Closer to the reef, harlequin shrimps, thorny seahorse, cleaner pipefish and orange-spotted pipefish added intricate detail. Tomato anemonefish, white-eye moray eels, giant moray eels and zebra moray eels occupied every crack, while octopus shifted colours between rocks. Headshield slugs, reticulated sapsucking slugs, ornate sapsucking slugs and Moyer’s dragonet were all present, alongside schools of five-lined snappers, twinstripe fusiliers and lunar fusiliers.

A vibrant yellow Tigertail Seahorse Hippocampus comes using its prehensile tail to anchor itself to colourful soft coral. — A bright yellow Tigertail Seahorse clings perfectly to the vibrant soft corals of the reef. | Renaud Liberge

A massive Giant Moray Eel peeks out from its rocky crevice, showing off its impressive size and patterned skin. | Frederique Bechet

The night dive revealed blunt decorated spider crabs, orange-spotted pipefish, boxer banded shrimps, Durban dancing shrimps, cleaner shrimps and pencil sea urchins. Ridged egg cowries and sixline soapfish appeared, while sleeping parrotfish, triggerfish locked into the reef and hunting moray eels completed the nocturnal scene.

Day 3 – Similan National Park, Koh Tachai & Koh Bon

Koh Tachai delivered strong currents and action-packed dives. Blacktip reef sharks cruised the reef, a hawksbill turtle passed by, and large schools of barracudas, dogtooth tuna and Spanish mackerel moved through the blue. African pompano, adult black and white snappers, lobsters and glassfish filled every level of the dive.

A Hawksbill sea turtle Eretmochelys imbricata swimming gracefully over a rocky reef slope in clear blue water. — A beautiful Hawksbill turtle glides effortlessly over the rugged reef terrain. | Frederique Bechet

A dense cloud of translucent glassfish hovering above a vibrant field of pink and purple soft corals on a healthy reef. — Thousands of tiny glassfish form a shimmering cloud over a garden of vibrant soft corals.

A massive swirling vortex of chevron barracuda schooling in the open ocean with sunbeams piercing through the water. — A shimmering silver tornado of barracuda creates a mesmerising spectacle in the deep blue. | The Smiling Seahorse

A sleek Blacktip reef shark Carcharhinus melanopterus patrolling a shallow reef plateau alongside a small school of yellow snappers. — A powerful Blacktip reef shark cruises past a colourful school of snappers along the reef edge. | Renaud Liberge

During the navigation to Koh Bon, dolphins came to greet the boat, riding the bow wave and adding a rare surface interval moment that stayed with everyone on board.

At Koh Bon Pinnacle, one group encountered a large shark in the deep, most likely a bull shark, while the pinnacle itself pulsed with schools of yellowback fusiliers and neon fusiliers. Coral groupers, peacock groupers, powder-blue surgeonfish and Indian sailfin tang added structure and colour to the reef.

On the North Ridge and West Ridge, reef life remained dense and dynamic, with anemone crabs, dogtooth tuna, rainbow runners and mackerels hunting through thick schools of glassfish, while wrasses, blennies and damsels filled every available space.

A Porcelain Anemone Crab Neopetrolisthes maculatus with its distinctive spotted pattern peeking out from the tentacles of its host anemone. — A tiny Porcelain Anemone Crab finds safety and shelter among the protective tentacles of its host. | Frederique Bechet

A large school of yellowback fusiliers Caesio teres swimming in unison through the bright blue waters of a healthy coral reef. — A vibrant school of fusiliers creates a flash of yellow and silver as they sweep across the reef. | The Smiling Seahorse

The blackwater dive introduced squids, salps sheltering small fish and pyrosomes drifting through the dark.

A translucent squid with shimmering iridescent spots and large eyes suspended against the pitch-black background of the open ocean at night. — A translucent squid glows with iridescent light while navigating the deep blackwater during its nightly migration.

A tiny larval juvenile fish with a transparent body and reflective metallic scales captured during a blackwater dive. — A tiny larval fish drifts through the darkness of the open ocean during a blackwater dive.

A glowing cylindrical pyrosome colony floating in the dark, providing shelter for a tiny juvenile fish nestled inside its opening. — A glowing pyrosome acts as a natural sanctuary for a tiny juvenile fish seeking protection in the vast open sea.

A silvery juvenile fish swimming alongside a large clump of organic detritus, known as marine snow, against the dark void of the ocean at night. — A tiny juvenile fish drifts through the darkness alongside nutrient-rich marine snow during its nightly journey.

A small iridescent squid with shimmering colourful spots on its mantle navigating through the pitch-black water. — Shimmering in the dark, a small squid displays a brilliant array of iridescent colours while moving through the blackwater.

A front-facing macro shot of a juvenile fish with large reflective eyes and translucent fins suspended in the blackwater. — Caught in the light, a juvenile fish reveals its delicate, translucent features and large reflective eyes.

Day 4 – Similan Islands & Crossing

At North Point, a Napoleon wrasse cruised past while squat shrimps, mantis shrimps and Durban dancing shrimps animated the reef. Anemone crabs, Clark’s anemonefish, moray eels and topsail drummers were joined by blueface angelfish, regal angelfish, butterflyfish and schools of fusiliers.

A Giant Moray Eel Gymnothorax javanicus sharing a rocky crevice with several bright red Pinecone Soldierfish. — A Giant Moray Eel rests within a sheltered reef alcove alongside a group of vibrant Pinecone Soldierfish. | Renaud Liberge

A Spearing Mantis Shrimp Lysiosquillina lisa peering out from its circular burrow in the substrate, showcasing its large complex eyes. — A formidable Spearing Mantis Shrimp keeps a watchful eye from the safety of its deep, sand-lined burrow. | Renaud Liberge

We then stopped at Island #8, also known as Donald Duck Bay, where white sand and granite boulders offered a striking contrast to the dives and a magnificent view from Sailrock offering sight of the blue and transparent water of the Similans.

A juvenile Blackspotted Boxfish Ostracion meleagris with its distinctive cuboid body and yellow-and-black spotted pattern swimming over a coral reef. — A juvenile blackspotted boxfish displays its striking geometric patterns while navigating the reef formations.

A tiny Squat Shrimp Thor amboinensis, also known as a Sexy Shrimp, perched on the reef with its tail arched upward. — The charismatic squat shrimp, famously known as the “sexy shrimp,” adds a splash of personality to the macro landscape.

A vibrant male Blue Ribbon Eel Rhinomuraena quaesita with its bright blue body and yellow dorsal fin extending from a burrow in the sandy reef floor. — A bright blue ribbon eel peeks out from its burrow, showcasing the dramatic colours found at Elephant Head Rock. | Renaud Liberge

Elephant Head Rock delivered dramatic topography with blue ribbon eels, adult yellow boxfish, juvenile blackspotted boxfish, red anthias, surgeonfish, blue dragon and giant trevallies weaving through the formations.

At West of Eden, two pipehorse fish hovered delicately while spearing mantis shrimps, squat shrimps, “sexy shrimps”, hawksbill turtle, blue dragon and a psychedelic batwing slug created a richly layered dive. Topsail drummers, fusiliers, snappers, angelfish, wrasses and parrotfish completed the reef.

We then crossed overnight towards Koh Lanta, leaving the granite islands behind.

Day 5 – Hin Daeng & Hin Mueang

Hin Mueang was full of life, with glassfish and juvenile fusiliers forming dense schools constantly targeted by hunting trevallies, African pompano and rainbow runners. Juvenile emperor angelfish, ghostpipefish, Bornella anguilla, Halgerda tesselata and phyllidia of various colours covered the reef.

Banded boxer shrimps, Durban dancing shrimps and cleaner shrimps filled every crevice, while titan triggerfish dug into the reef and redtooth triggerfish hovered above. Topsail drummers completed the scene.

A juvenile Emperor Angelfish Pomacanthus imperator with its striking pattern of concentric blue, white and black circles swimming against a backdrop of pink soft corals. — A young Emperor Angelfish displays its hypnotic swirling patterns while navigating a garden of soft corals. | Renaud Liberge

Multiple Bornella anguilla nudibranchs with intricate branching cerata crawling over red algae and reef substrate. — These fascinating Bornella Anguilla nudibranchs blend into the reef as they search for food among the red algae. | Renaud Liberge

A large Titan Triggerfish Balistoides viridescens with its characteristic scales and powerful jaw swimming near a bright orange sea fan. — The imposing Titan Triggerfish patrols the reef edge near a vibrant orange gorgonian sea fan.

A red and white Ghost Pipefish Solenostomus paradoxus hovering near an orange sponge, perfectly mimicking its surroundings. — A master of disguise, this Ghost Pipefish hides in plain sight against the colourful reef backdrop. | Renaud Liberge

Hin Daeng delivered ghostpipefish, Glossodoris cincta and its eggs, ornate elysia, giant moray eels hunting in the shallows, Clark’s anemonefish, anemone crabs and tiger egg cowries. Batfish, fusiliers, snappers, surgeonfish, sweetlips and reef fish filled the water column.

A Glossodoris cincta nudibranch crawling over a reef, displaying its mottled brown body and distinctive multicoloured frilled edge. — A Glossodoris Cincta nudibranch displays its beautifully ruffled and colourful mantle edge while exploring the reef. | Frederique Bechet

A tiny yellow and black striped Tiger Egg Cowrie perched on a branch of pale pink soft coral. — A vibrant Tiger Egg Cowrie stands out against the delicate branches of a soft coral host. | Frederique Bechet

The night dive intensified the atmosphere with multiple giant moray eels hunting, small octopus camouflaging along the wall, and a constant movement of crabs and shrimps across the reef.

Day 6 – Koh Tarutao National Park

At 8 Mile, excellent visibility revealed a very friendly marble grouper who looked like he was mixed with a barramoundi, great barracuda, schools of scribbled filefish, juvenile emperor angelfish, juvenile blue-ringed angelfish, stonefish, yellowtail barracuda and schools of giant trevallies, alongside fusiliers, snappers, surgeonfish and reef fish.

A large Marbled Grouper Epinephelus fuscoguttatus displaying its intricate brown and white mottled pattern against a deep blue ocean backdrop. — A Marbled Grouper shows off its stunning natural camouflage while patrolling the reef. | Renaud Liberge

A Scribbled Filefish Aluterus scriptus with its distinctive elongated body and blue-spotted pattern swimming over a healthy coral reef. — The uniquely patterned Scribbled Filefish glides gracefully above a bustling reef community.

A well-camouflaged Scorpionfish resting on a rocky seabed surrounded by vibrant purple soft corals. — Blending perfectly into its surroundings, this Scorpionfish waits patiently among the corals for passing prey. | Renaud Liberge

A juvenile Blue Ringed Angelfish Pomacanthus annularis featuring brilliant blue and white concentric stripes on its deep blue body. — The electric blue patterns of a juvenile Blue Ringed Angelfish provide a striking pop of colour against the reef. | Frederique Beche

Stonehenge offered three tigertail seahorses, including one black pregnant individual, surrounded by bird wrasse, moon wrasse and sixline wrasse, along with parrotfish, scorpionfish, butterflyfish and damsels.

A Tigertail Seahorse Hippocampus comes with a dark mottled pattern clinging to a reef structure near vibrant red sea fans. — A master of camouflage, this Tigertail Seahorse blends seamlessly into the reef textures. | Frederique Bechet

Two slender Razorfish Aeoliscus strigatus swimming in their characteristic vertical head-down position over a sandy seabed. — A pair of Razorfish navigate the currents in their unique vertical swimming style.

A close-up of a Peacock Flounder Bothus mancus showing its blue-ringed patterns and both eyes positioned on the top side of its flat body. — The intricate, flower-like patterns of a Peacock Flounder provide incredible camouflage against the sandy bottom.

At Steps, the sunset dive featured yellow-scribbled pipefish, Kuhl’s blue-spotted stingray, bamboo shark, flounder and razorfish, alongside fusiliers, goatfish, sweetlips, surgeonfish and reef fish settling into the evening light.

Day 7 – Koh Lanta National Park

Hin Mueang again delivered intense action, with schools of dogtooth tuna, Spanish mackerel, rainbow runners and mackerels hunting through glassfish and juvenile fusiliers. Batfish hovered nearby, while two yellow ghostpipefish and topsail drummers added structure.

Hin Daeng revealed yellow and black ghostpipefish and a juvenile hawksbill turtle surfacing for air before resting. Clark’s anemonefish, anemone crabs, ornate sapsucking slugs and reef life filled the dive.

A close-up of a Hawksbill sea turtle (Eretmochelys imbricata) showing its distinctively patterned head and shell as it swims over a vibrant coral reef. | Renaud Liberge

A large craggy limestone karst island rising sharply from a calm deep blue sea under a clear sky. — The iconic limestone cliffs of Koh Haa tower over the crystal-clear waters of the Andaman Sea. | Renaud Liberge

A large red hermit crab partially emerged from its protective seashell on a sandy and rocky seabed. — A resilient hermit crab carries its portable home across the sandy ocean floor in search of food. | Renaud Liberge

A vibrant underwater scene featuring several purple-based sea anemones surrounded by soft pink corals and dark sea urchins. — A colourful underwater garden thrives with purple anemones and delicate soft corals at the base of the reef.

A sleek silver dogtooth tuna swimming through the dark deep blue open water. — A powerful dogtooth tuna patrols the deep blue water near the island’s steep drop-offs.

At Cathedral, massive Glossodoris hikuerensis, Halgerda stricklandi, Halgerda candy, Verconia alboannulata (Noumea alboannulata), Bornella anguilla, a juvenile hawksbill turtle with a damaged shell, titan triggerfish carrying shells, bannerfish, Moorish idols, giant moray eel, longfin batfish and pinnate batfish created a rich and layered scene.

At the Cheminee, ghostpipefish, Cuthona sibogae, tiger cowrie eggs, giant moray eels, cave fish, sweetlips, snappers, yellowback fusiliers, neon fusiliers, glassfish, ornate elysia, scorpionfish, parrotfish and anemonefish filled the tunnel.

The day ended with our traditional BBQ on board, under calm seas and a sky full of stars.

A macro shot of an Ornate Elysia nudibranch Elysia ornata featuring a translucent green body with a distinct black and gold frilled margin crawling over a textured reef. — The Ornate Elysia nudibranch displays its stunning gold-rimmed parapodia while navigating the diverse reef systems of Koh Phi Phi. | Renaud Liberge

A translucent jellyfish with bright pink internal radial canals and long flowing tentacles drifting through the dark blue water column. — A ghostly jellyfish pulses through the deep blue, its pink interior glowing against the shadows of the Andaman Sea. | Renaud Liberge

A vibrant Trinchesia sibogae nudibranch with a purple body and numerous pink, yellow-tipped cerata perched on a delicate hydroid branch. — Adding a burst of colour to the macro world, the Trinchesia sibogae nudibranch shows off its brilliant pink and yellow-tipped cerata. | Frederique Bechet

A bright yellow Tiger Tail Seahorse Hippocampus comes with dark banding on its tail, using its prehensile tail to anchor onto a red gorgonian sea fan. — A vivid yellow Tiger Tail Seahorse finds a perfect anchor point among the branches of a colourful gorgonian sea fan. | Renaud Liberge

Day 8 – Koh Phi Phi & Final Dive

Bida Nok offered blacktip reef sharks, tigertail seahorse, two ghostpipefish, schools of five-lined snappers, giant moray eels, batfish and schools of fusiliers moving across the reef alongside butterflyfish, surgeonfish and parrotfish.

At King Cruiser wreck, the sunken ferry now acts as a thriving artificial reef, covered in life. Schools of yellowback fusiliers, bigeye trevallies, schools of jacks and snappers circled the structure, while lionfish and groupers, sweetlips and reef fish occupied every level of the wreck.

Closer to the structure, macro life revealed itself in layers: Hypselodoris infucata, Glossodoris atromarginata, Chromodoris aureopurpurea, Hypselodoris sp. 3 and Flabellina rubrolineata decorated the surfaces, turning the wreck into a vibrant underwater mosaic where small details were just as captivating as the schooling fish above.

A vibrant pink Verconia alboannulata nudibranch with a white border and bright orange rhinophores and gills crawling over a textured reddish-brown reef. — The striking pink hues of a Verconia alboannulata nudibranch stand out against the rocky substrate, showcasing the intricate detail of macro life. | Frederique Bechet

A detailed illustrated map of the King Cruiser wreck showing sections including the wheelhouse, passenger deck and car deck, with schools of fish around the structure. — A comprehensive map of the King Cruiser wreck highlights key features and depths for divers exploring this massive artificial reef.

We ended the trip at Phuket Marin Charter Pier, saying goodbye after a week rich in encounters, diversity and unforgettable underwater moments.

From open-ocean encounters to the smallest hidden reef life, this journey captured the full spectrum of Andaman diving — shaped by rhythm, diversity, and the quiet magic of life below the surface.

See you soon, fellow divers.

Pictures from Renaud Liberge & Frederique Béchet (pictured below) present on this trip and others from Franck Fogarolo.