This is one of the rarest and most powerful spawning expeditions we offer—bringing together two of Palau’s most extraordinary natural events into a single, perfectly timed journey.
Only a few times a year—March, April and May —the lunar cycles align to make this possible. Miss these windows, and the opportunity disappears.
Only a full immersion of a liveaboard on Palau Siren, with a schedule built around early morning dives and optional late-night sessions—can truly ensure you’re in the water exactly when the action peaks.
We begin with the explosive aggregation of the Blue-lined Sea Bream.
Over several days, you’ll witness what is believed to be the largest aggregation of this species ever discovered, with over 30,000 fish gathering in a dense, fast-moving mass. We spend several days diving the aggregation watching the moment the school builds. Then one early morning its time, the school tightens, surges, and erupts into a high-energy spawning event—an overwhelming wall of movement, scale, and intensity.
Then, just as that spectacle reaches its peak, we shift gears.
We transition into the raw, primal power of the Bumphead Parrotfish spawning event. Here, hundreds to over a thousand giant fish gather, moving with slow, deliberate force before bursting into action as they spawn—creating a completely different, yet equally unforgettable experience.
Two completely different rhythms.
One perfectly timed expedition.
To witness both of the largest known aggregations of these species in a single trip is something very few divers will ever experience.
Once the spawning events have concluded, we continue exploring the very best of Palau—diving manta ray cleaning stations, shark-filled channels, dramatic caverns, blue holes, swim-throughs, and even the surreal waters of marine lakes.
Massive schools. Giant fish. Perfect timing.
This is not just a dive trip—it’s a front-row seat to some of the greatest natural events in the ocean.
Over the course of the expedition, you’ll:
Dive the primary aggregation site at the peak of the new moon cycle
Experience multiple spawning dives in high-energy conditions
Explore Palau’s world-class reefs, blue holes, corners, and iconic drift dives
Gain real understanding through daily briefings and in-depth presentations
Expect early mornings, currents, and serious diving—this is for those who want more than just beautiful reefs.
All of our unique Palau itineraries are hosted by Palau Siren Liveaboard. With a liveaboard diving experience, you maximizing your time on the best sites when conditions are right.
Massive fish. Explosive action. Perfect timing.
This is Palau at its wildest…….Miss the moon… and you miss the moment.
Our Palau expeditions are designed for passionate divers who want to experience some of the most spectacular natural events in the ocean.
You do not need to be a technical diver, a professional photographer, or someone with hundreds of dives — but you do need to be a confident diver.
We require a minimum of 50 logged dives and a PADI Advanced Open Water certification (or equivalent). Guests should also have previous experience diving in currents, as many of Palau’s most exciting encounters happen where ocean movement brings marine life together.
Palau is famous for its drift diving, reef hooks, spawning aggregations, and fast-changing conditions. Our guides are there to position the group safely and at the right moment, but divers should already be comfortable controlling their buoyancy, descending without difficulty, and diving as part of a group in open ocean environments.
For specialty experiences such as bumphead parrotfish spawning dives, camouflage grouper night spawning dives, and blackwater dives (when offered), previous night diving experience is required. These are some of the most unique wildlife encounters on the planet, but they require confidence in low-light conditions, good awareness, and precise buoyancy control.
You do not need thousands of dives. You just need solid experience, good dive skills, and a sense of adventure.
The 40m S/Y Palau Siren was designed by divers for divers to provide superior ease and comfort.
Aboard Palau Siren, scuba enthusiasts will explore pristine, remote dive sites and enjoy lavish accommodations.
The Palau Siren crew of 12 is on hand to ensure guest satisfaction for up to 16 divers.
This intimate liveaboard offers ample space including 8 large cabins equipped with individual climate control, entertainment system and en suite bathrooms.
The SY Palau Siren also features an air-conditioned lounge with cocktail bar, sofas, 42 inch flat screen and movie network.
Massage service is available daily. The decks feature a covered outdoor dining area where meals and refreshments will be served buffet style throughout the day and an upper level sun deck with cushioned loungers.
A large shaded diving deck provides individual stations and personal storage lockers.
Guests are also provided with tanks, weights, BCD, regulator, 3mm wetsuit, mask and fins free of charge.
The main lounge offers a fully equipped camera and video station of professional quality.
Palau Siren schedules year round dive trips offering scuba divers the thrill of deep dives, the tranquility of drift dives and the opportunity to encounter huge numbers of pelagic.
Book now to dive the spectacular Palau waters on a Palau Siren liveaboard diving holiday.Large air-conditioned cabins each with their own personal audio-visual entertainment system and ensuite bathrooms with hot water.
All rooms are lavished with luxury extra's including bathrobes, hair dryers, towels, individually controlled mood lighting and individual controls for your air-conditioning unit
Deluxe Twin Cabins – B3, B5, B6 & B7 / B4
The Deluxe Twin Cabins on the Palau Siren are thoughtfully designed to combine comfort and functionality.
Cabins B3, B5, and B7 offer flexible twin or double-sharing arrangements, while B4 features cozy bunk beds for twin sharing.
Each cabin provides ample living space, smart storage solutions, and a relaxing atmosphere, ensuring two guests can enjoy both privacy and convenience during their underwater adventures.
Modern amenities and a serene design make these cabins a perfect retreat after a day of diving in Palau’s stunning waters.
Deluxe Double Cabins – B1 & B2
The Deluxe Double Cabins on the Palau Siren feature a comfortable queen-sized bed, providing a perfect space for two guests to relax after a day of diving.
Thoughtfully designed with both comfort and practicality in mind, each cabin offers generous living space, smart storage solutions, and a serene ambiance.
These cabins combine cozy elegance with functionality, ensuring that every guest enjoys a restful and convenient retreat in the heart of Palau’s breathtaking waters.
Sam’s Tours, Koror at 17:00
Disembarkation: Sam’s Tours, Koror at 10:00
Transfer to Sam's Tours from Koror Airport* or a local hotel is provided free of charge on embarkation day. Pick-up time from local hotels is usually between 16:30 and 17:00.
*Airport pick-up is dependent on flight arrival time. Guests arriving in the early hours of the morning on embarkation day need to arrange hotel accommodation.
Transfer from Sam's Tours to local hotels or Koror Airport is provided free of charge upon disembarkation at 10:00 only.
Guests with evening or night flight departures who have made arrangements for day use at local hotels will be transferred from Sam's Tours to the hotel but are responsible for arranging their transfers from the hotel to the airport.
Likewise, guests who wish to leave their luggage at Sam's Tours and explore downtown Koror before their departure are also responsible for
arranging their own transport to the airport.
Marine Park Fees, drills and all safety procedures are carried out on Day 1
Palau Islands permits and fees: (payable onboard only)
7 nights: 230 USD per person
10 nights: 300 USD per person
These fees are mandatory and subject to change without notice. The applicable amount at the
time of your liveaboard departure will be added to your onboard bill to be paid before disembarkation.
The Ulong area is one of Palau’s most diverse regions, offering a completely different experience from the famous walls of the outer reef. Here we explore a combination of channels, coral gardens, historical sites, and current-driven dives where Palau’s marine life is at its very best.
Ulong Channel is one of Palau’s signature dives — a beautiful drift through a natural underwater corridor lined with some of the healthiest hard coral formations in Micronesia. When the currents are moving, grey reef sharks patrol the entrance, schools of jacks and barracuda gather in the blue, and divers finish by flying effortlessly through the channel past huge lettuce coral formations.
The area is also home to sites such as Siaes Corner, Siaes Tunnel, and Shark City, offering dramatic walls, caverns, shark action, schooling fish, and incredible wide-angle photography opportunities. Every dive here is dictated by the tides, and when conditions align, Ulong delivers some of Palau’s most exciting underwater encounters.
Later in the expedition we return to this special area for one of Palau’s greatest natural events — the Bumphead Parrotfish spawning aggregation. Before sunrise, hundreds of these prehistoric-looking fish gather together, following ancient rhythms controlled by the moon and tides. Witnessing this behavior is one of the true highlights of diving Palau and exactly the kind of rare ocean event our expeditions are designed around.
Day 2: Departure from Malakal Harbour after breakfast followed by a check dive, and up to 3
subsequent dives, as outlined below.
Your Cruise Director will schedule up to 4 dives per day; 3 day dives and either a sunset or a night dive. A typical diving day is scheduled as follows:
● 6.30am - Light Breakfast followed by a briefing & Dive 1
● 9.30am - Full Breakfast, relaxation followed by briefing & Dive 2
● 12.00pm - Lunch, relaxation followed by briefing & Dive 3
● 4.00pm - Snack
● 6.00pm - Briefing for Sunset or Night dive
● 7.30pm Dinner
The Ngemelis Island area is home to some of Palau’s most legendary dive sites and represents everything that makes this destination world-famous — dramatic walls, powerful currents, huge schools of fish, healthy coral reefs, and encounters with some of the Pacific’s most iconic marine life.
This is where we find sites such as Blue Corner, Blue Holes, New Drop Off, Big Drop Off, and German Channel. Each site offers something completely different — from hooking in at Blue Corner watching grey reef sharks cruise effortlessly in the current, to descending through the cathedral-like shafts of Blue Holes, or exploring vertical walls covered in sea fans, soft corals, and marine life.
German Channel is one of Palau’s most exciting cleaning stations, where manta rays can appear from the blue and circle gracefully above the reef. Large schools of barracuda, jacks, snapper, turtles, Napoleon wrasse, and reef sharks are regular encounters throughout this area, making every dive unpredictable and full of possibilities.
The Ngemelis reefs are a perfect example of why Palau remains one of the world’s greatest dive destinations. Here, every dive is shaped by the ocean — the tides, currents, and seasons deciding what we may encounter. No two dives are ever the same, and that is exactly what makes this area so special.
Day 4: Departure from Ulong Island Area after lunch followed by a sunset dive on arrival to Ngemelis Island anchorage area.
The following days, your Cruise Director will schedule up to 4 dives per day; 3 day dives and either a sunset or a night dive.
A typical diving day is scheduled as follows:
● 6.30am - Light Breakfast followed by a briefing & Dive 1
● 9.30am - Full Breakfast, relaxation followed by briefing & Dive 2
● 12.00pm - Lunch, relaxation followed by briefing & Dive 3
● 4.00pm - Snack
● 6.00pm - Briefing for Sunset or Night dive
● 7.30pm Dinner
Located at the southern edge of Palau’s reef system, Peleliu is one of the most remote and exciting diving areas in Palau. Famous for its powerful currents, deep walls, and incredible marine encounters, this area is also home to one of the ocean’s most spectacular natural events — the annual gathering of Blue-Lined Sea Bream.
Rather than moving the Palau Siren south, we remain anchored in the protected waters of Koror and travel to Peleliu by private speedboat. This allows us to reach the spawning grounds quickly, with the journey taking approximately 20 minutes, while keeping the comfort of the liveaboard as our home base.
Timed around the new moon, thousands of Blue-Lined Sea Bream gather along the reef edge, creating one of the largest fish aggregations found anywhere in Palau. Huge schools build over several days as the fish prepare to spawn, attracting grey reef sharks and other predators drawn by this incredible concentration of marine life.
For two consecutive mornings, we travel to Peleliu to focus entirely on this event. Each day we complete two dives dedicated to the aggregation, giving us multiple opportunities to witness the peak behavior as conditions, tides, and timing come together.
This is expedition diving at its best — not simply visiting a dive site, but understanding when nature’s greatest moments happen and positioning ourselves to be there when they do.
Day 6: Repositioning South Towards Peleliu & Ngemelis Island
After our final dives in the Ulong area, the Palau Siren begins her journey south, leaving the protected lagoons of Ulong as we reposition closer to the legendary reefs of Ngemelis and Peleliu.
This afternoon is all about preparing for the next stage of the expedition, where the focus shifts from Palau’s classic reef diving to one of the ocean’s greatest natural spectacles — the Blue-Lined Sea Bream spawning aggregation.
After arriving at our new anchorage near Ngemelis Island, we finish the day with a relaxed sunset dive surrounded by some of Palau’s most famous reefs before the early morning adventures ahead.
Then the next day naturally flows:
Day 7–8: Peleliu Blue-Lined Sea Bream Aggregation
Before sunrise, we leave the Palau Siren by private speedboat and travel south to Peleliu...
The following days, your Cruise Director will schedule up to 4 dives per day; 3 day dives and a sunset dive.
A typical diving day is scheduled as follows:
● 6.30am - Breakfast followed by a briefing & Dive 1
● 9.30am - Full Breakfast, relaxation followed by briefing & Dive 2
● 12.00pm - Lunch, relaxation followed by briefing & Dive 3
● 4.00pm - Snack
● 6.00pm - Briefing for Sunset or Night dive
● 7.30pm Dinner
As our expedition enters its final days, we return to the Ulong area — but this time with a very different focus. Earlier in the trip we explored Ulong’s famous channels, walls, and reefs; now we come back as the moon phase and tides align for some of Palau’s most extraordinary natural events.
Our main focus is the Bumphead Parrotfish spawning aggregation, one of the most unique wildlife encounters in the ocean. Before sunrise, hundreds of these prehistoric-looking fish gather together in the shallow reefs, following ancient rhythms controlled by the moon and tides. Watching the build-up, courtship behavior, and explosive spawning event is a rare experience that very few divers ever witness.
During this period, we also have additional opportunities to revisit Shark City, where the Blue-Lined Sea Bream aggregation may still be active. These huge gatherings of fish create incredible scenes as the reef comes alive with movement, energy, and predator activity.
As the expedition comes to a close, we continue exploring the best conditions Ulong has to offer, from exciting drift dives through Ulong Channel to special night dives where we search for nocturnal marine life, including several species of spawning groupers. It is the perfect way to finish our journey — letting the moon, tides, and ocean decide the final surprises.
Day 9: We shall finish our expedition diving two days back at Ulong Island area for the Bumphead Parrotfish Spawning subsequent dives, as outlined below.
Your Cruise Director will schedule up to 4 dives per day; 3 day dives and either a sunset or a night dive. A typical diving day is scheduled as follows:
● 5.30am - Light Breakfast followed by a briefing & Dive 1
● 8.30am - Full Breakfast, relaxation followed by briefing & Dive 2
● 12.00pm - Lunch, relaxation followed by briefing & Dive 3
● 4.00pm - Snack
● 6.00pm - Briefing for Sunset or Night dive
● 7.30pm Dinner
Day before disembarkation:
For your last full day on board, we schedule up to 3 dives* before the boat cruises back to
Malakal Harbour, where it will remain at anchor overnight.
Disembarkation day: Following breakfast on board, disembarkation is scheduled for 10:00.
*We kindly request that guests check their flight departure times to ensure they leave a
minimum of 24 hours between their final dive and their flight home.
Fishing is NOT permitted on Palau Siren, under any circumstances.
In the days leading up to the new moon, something remarkable begins to take shape across Palau’s outer reefs and channels.
From the lagoon and surrounding reef systems, hundreds, often nearly a thousand Bumphead Parrotfish (Bolbometopon muricatum) begin to gather, slowly building in numbers as they prepare for one of the ocean’s most extraordinary spawning events.
We start our expedition ahead of the new moon, diving Palau’s iconic current-swept sites as the anticipation builds.
With each passing day, the signs become clearer—the fish are arriving, the energy is shifting, and the stage is being set.
Then comes the moment.
Before sunrise, we head out. As the first light breaks over the horizon, we descend into position and wait.
Out of the blue, they appear.
A steady procession of massive bumpheads begins to pour out of the lagoon, flowing onto the reef like a living river—building, layer by layer, into a powerful aggregation. What starts as a slow, deliberate movement quickly transforms into a surge of energy, as the entire group pushes forward to spawn, releasing clouds of life into the water column.
It’s not chaotic like other spawning events—it’s something different.
There’s a rhythm to it. A flow. A raw, majestic choreography that feels almost unreal to witness.
This is one of nature’s true spectacles—quietly powerful, deeply primal, and unforgettable.
Miss it… and you’d never know it happened…………Be there… and it stays with you forever.
Some events in the ocean cannot be forced. They cannot be predicted by a calendar alone. They happen when the moon, tides, and currents all come together perfectly.
The Blue-lined Sea Bream spawning aggregation is one of Palau’s greatest natural spectacles.
For most of the month, these fish are spread throughout the reef system. But as the new moon approaches, something changes. Driven by an ancient instinct, thousands begin their journey toward specific outer reef sites, forming one of the largest and most impressive fish aggregations in the Pacific.
Over several days, the numbers continue to build.
The reef transforms.
Small groups become schools. Schools become rivers of fish. Eventually, the entire reef edge is alive with movement as countless sea bream hold position in the current, waiting for the exact moment.
Our expedition is timed around this narrow natural window.
Before dawn, we leave in darkness and make our way toward the spawning grounds. There are no guarantees in nature — only knowledge, experience, and understanding the conditions that give us the best chance.
As the sun begins to rise, the ocean changes.
Thousands of sea bream lift away from the reef and move together as one. The calm suddenly disappears as the aggregation erupts into a spectacular spawning rush, filling the water column with life.
For a few unforgettable minutes, you are surrounded by one of the ocean’s greatest reproductive events.
But the sea bream are not alone.
Sharks patrol the edges, waiting for their opportunity. Bull sharks, oceanic blacktips, and reef sharks move through the chaos as the entire ecosystem responds to this incredible concentration of life.
Months of preparation. Days of waiting. Minutes of action.
Timing is everything.
During our expedition, weather and ocean conditions permitting, we will also have the opportunity to experience up to two very different blackwater night dives — one BONFIRE STYLE near a deep drop off and one TRUE BLACKWATER offshore in the deep ocean.
Blackwater diving gives us a rare window into one of the least-seen parts of the marine world — the nightly migration of tiny ocean creatures rising from the depths. Throughout our journey we have focused on spawning aggregations, watching thousands of fish gather and release eggs and sperm into the water column. Blackwater diving allows us to continue that story, searching for the next stage of this incredible journey as new life begins drifting through the ocean.
Our inshore blackwater dive takes place within Palau’s protected lagoon system. These dives often reveal the early larval stages of reef animals that will eventually settle back onto the very reefs we have been exploring. Tiny juvenile fish, larval crustaceans, cephalopods, and other planktonic creatures appear in forms completely different from their adult stages.
Our offshore blackwater dive takes us beyond the reef edge, suspended over much deeper water. Here we enter the world of the deep scattering layer — an enormous vertical migration where strange and rarely seen animals travel upwards from the depths each night. Transparent creatures, deep-water larvae, squid, jellyfish, and alien-like life forms drift past our lights in a world few people ever experience.
For us, blackwater diving completes the circle. During this expedition we may witness multiple species gathering in huge numbers to reproduce, from Blue-Lined Sea Bream to Bumphead Parrotfish. These spawning events represent the very beginning of the next generation — and blackwater diving offers a glimpse into what happens after those tiny eggs enter the ocean currents and begin their incredible transformation into life on the reef.
Richard Barnden is the founder of Unique Ocean Expeditions, a specialist scuba diving travel company created to bring divers closer to some of the ocean’s most extraordinary natural events. An award-winning underwater photographer, Richard has spent nearly two decades exploring, guiding, and documenting marine life throughout the Pacific Ocean.
After more than 20 years working in the waters of Palau, Richard developed a deep understanding of the timing, locations, and conditions needed to witness some of nature’s rarest underwater encounters. His work focuses on predictable marine events shaped by moon phases, tides, and seasonal behavior — including fish spawning aggregations and blackwater night diving.
Through years of observation and photography, Richard has documented events that few divers ever experience, from mass spawning aggregations involving thousands of fish to the mysterious larval stages of marine life found during blackwater dives.
Unique Ocean Expeditions was created to share these moments with small groups of passionate divers — combining experience, patience, and timing to be in the right place, at the right time.
Richard moved to Palau in his early twenties as a video pro and later became the cruise director of multiple live-aboards where he continued his passion of filming. After building a large collection of data and photos of spawning aggregations which at the time he knew very little about he went on to spend the next decade trying to understand their predictabilities.
Richard now organises multiple spawning expeditions in Palau each year, these spawning expeditions are tailored around lunar phases to observe fish reproduction mainly during the early hours of the morning. By night Richard spends most of his time with his guests photographing plankton and their environments, a relatively new kind of night dive called blackwater diving.
His long-term research has played a key role in unlocking some of the spawning patterns of species such as the camouflage grouper and Lutjanus bohar. As a photographer, he is well known for capturing these fleeting, high-energy moments—from explosive spawning events to the surreal, otherworldly creatures encountered during blackwater dives.
Combining deep field knowledge with a relentless pursuit of the extraordinary, Richard continues to push the boundaries of exploratory diving—bringing his guests face-to-face with some of the ocean’s most spectacular and least-understood phenomena.
RICHARD BARNDEN EXPEDITION LEADER