The buoys drift away, the lagoon opens.
The engine barely hums before the shoreline slips behind us. On board, the air still carries the weight of heat, but ahead, the horizon turns liquid, almost unreal. I’m with Seablue Safari, guided by Mathias, a pilot who knows these waters the way one knows a familiar path. We’ve barely left the coast when he begins to explain. Here, nothing is accidental. Mayotte’s lagoon is not simply a sheltered body of water. It is a slow construction, born from fire, shaped by coral, and carved by currents. To understand it, you have to go back long before the mantas, long before the dolphins — back to the very origin of the island. A landscape that began forming millions of years ago, with its present contours gradually taking shape around 3 to 4 million years ago. 
Origins: an island born from fire
Long before it became a lagoon, Mayotte was a volcano. Located in the Comoros archipelago, the island formed through volcanic activity estimated between 8 and 10 million years ago. Like many tropical islands, it was later colonized by corals — organisms capable of building, generation after generation, vast living structures. Around the island, corals progressively formed a barrier reef. Then, slowly, almost imperceptibly, the volcanic mass began to subside. The corals, however, continued to grow upward toward the light, maintaining their position near the surface. This mechanism — first described in the 19th century by Charles Darwin — explains the formation of tropical lagoons: a sinking island, a rising reef, and between them, a protected body of water. In Mayotte, this process created one of the largest enclosed lagoons in the world. 
A lagoon is not a lake
At first glance, the lagoon may appear calm, almost still. But that impression is deceptive. A lagoon is a living system, constantly in motion. Protected by a barrier reef, it remains connected to the open ocean through openings known as passes. These passes allow:
Without them, the lagoon would stagnate. With them, it breathes. 
The S Pass — a defining feature of Mayotte
Among these openings, some have become iconic. One of them is the famous S Pass. From above, it traces a sinuous curve through the reef barrier. Below the surface, it acts as a channel where water masses rush in, accelerate, slow down, and mix. Its shape is no accident. While currents and erosion play a major role in carving the pass, its trajectory may also be influenced by an older structure. During periods when sea levels were lower, parts of what is now submerged were exposed, shaped by relief and freshwater flows. An ancient valley, gradually flooded as sea levels rose, may have guided the formation of this channel. Since then, ocean currents have taken over, widening, sculpting, and maintaining this passage, which has become essential to the lagoon’s circulation. These areas concentrate life: fish, predators, plankton. They are corridors of movement — but also zones of encounter. 
How passes are formed
Passes are not simple gaps in the reef. They are zones where energy concentrates. They form where:
Over time, these zones widen, deepen, and become permanent channels. 
A volcano still active beneath the sea
But Mayotte’s geological story does not end there. In 2018, a new underwater volcano was discovered several dozen kilometers east of the island, at a depth of more than 3,000 meters. A recent formation, born from intense activity, reminding us that the region remains geologically active. This volcano did not shape the present lagoon — it is far too recent — but it highlights an essential reality: Mayotte is not a static landscape. It is a territory still in motion. 
A fragile balance
Today, Mayotte’s lagoon is an exceptional ecosystem. Seagrass beds, coral reefs, sandy areas and passes form a complex network where each element plays a role. But this balance is fragile. Human pressure, pollution, overfishing, and climate change all have the potential to disrupt exchanges, alter balances, and weaken the system. Passes, in particular, are critical zones. They concentrate life — but also impact. 
Between story and reality
The engine cuts. Silence settles. Around us, the lagoon appears still, almost frozen. This is where Mathias chose to tell his story. Not the one about mantas or dolphins, but the deeper one — of a landscape shaped over millions of years. He speaks of another feature of Mayotte’s lagoon: its double barrier reef, a rare structure on a global scale, parts of which have collapsed over time, revealing a system as complex as it is fragile. In recent years, political ambition has grown: to have the lagoon recognized as a UNESCO World Heritage Site. On paper, such recognition could offer additional protection to this unique ecosystem. But for Mathias, who has navigated these waters for more than thirty years, reality is more nuanced. Over time, he has watched the lagoon change. Construction spreading. Waste accumulating. Wastewater finding its way into the sea. And more recently, additional human impacts placing further pressure on an already fragile system. Without raising his voice, he speaks of a gap. Between announcements and reality. Between image and ground truth. In this context, some see a strong signal. He sees a risk: that recognition becomes a showcase, without always being matched by the means needed to protect what it claims to preserve. The engine starts again, softly. The boat glides over water of unreal clarity. Around us, the lagoon remains what it has always been: a space of life, balance, and raw beauty. So Mathias takes us further. To observe. To understand. To experience. While it is still possible. Because some wonders are not meant to be admired. They are meant to be protected. 
The engine starts again, softly.
The boat glides over water of unreal clarity. Around us, the lagoon remains what it has always been: a space of life, balance, and raw beauty. So Mathias takes us further. To observe. To understand. To experience. While it is still possible. Because some wonders are not meant to be admired. They are meant to be protected. Mayotte Lagoon: Key FactsIs Mayotte one of the largest lagoons in the world?Yes. Mayotte is widely described as one of the largest enclosed coral lagoons in the world, with estimates often ranging from more than 1,000 km² to around 1,500 km² depending on the source and measurement method. Its reef system is also remarkable because it includes a rare double barrier reef. What are some of the world’s largest lagoon systems?The world’s largest lagoon systems include New Caledonia’s lagoon, Lagoa dos Patos in Brazil, Mar Menor in Spain, Laguna Madre in Mexico and the United States, and Mayotte’s enclosed coral lagoon. These systems are difficult to rank precisely because some are coastal lagoons, others are coral reef lagoons, and their measured surface areas vary by definition. Why is Mayotte’s lagoon so deep?Mayotte’s lagoon is unusually deep because it formed around an ancient volcanic island that gradually subsided while coral reefs continued to grow upward toward the light. This long geological process created a wide and deep protected lagoon between the island and the outer reef barrier. Why are reef passes important in Mayotte?Reef passes are essential because they connect the lagoon to the open ocean. They allow water renewal, nutrient exchange, larval dispersal, and the movement of marine life. In Mayotte, passes such as the S Pass are also biodiversity hotspots where currents concentrate life. What makes Mayotte’s lagoon fragile?Mayotte’s lagoon is vulnerable because its ecological balance depends on water quality, healthy coral reefs, seagrass beds, and functioning reef passes. Pollution, wastewater, plastic waste, coastal construction, overfishing, climate change, and extreme weather events can all weaken this balance. Between fear, function, and the fragile architecture of the reef The gaze  A predator shaped by misunderstanding For decades, moray eels have been cast as the villains of coral reefs — secretive, aggressive, unpredictable. Their serpentine bodies and exposed teeth make them easy subjects for fear. Yet the reality is quieter, almost restrained. Morays are not hunters of opportunity in the open water. They are ambush specialists, built for a life between shadows. Their elongated bodies allow them to navigate narrow crevices, anchoring themselves within the reef rather than roaming it. The constant opening of their mouth — often interpreted as a threat display — is simply a physiological necessity. Unlike many fish, morays rely on this motion to push water across their gills. They are not signaling danger. They are surviving. Most incidents involving humans are not acts of aggression, but of confusion — a misplaced hand, a conditioned response to feeding, a moment where the boundary between species is crossed without understanding. Remove the myth, and what remains is not a menace, but a specialist — precise, adapted, and remarkably controlled.  Life between rocks To understand a moray eel, you have to understand where it lives. Not the reef as a landscape, but the reef as a structure — a labyrinth of cavities, overhangs, and fractures. Morays do not simply inhabit reefs; they depend on their architecture. Every crevice is shelter. Every shadow is strategy. This dependency makes them more vulnerable than they appear. As reefs degrade — through warming oceans, physical destruction, or ecological imbalance — the complexity that sustains species like morays begins to collapse. A reef can still look alive from a distance, yet be hollowed out where it matters most. And in those missing spaces, something disappears. Not always visibly. Not immediately. But inevitably...  Invisible alliances For an animal often defined by its teeth, the moray eel participates in some of the reef’s most delicate interactions. Cleaner shrimp — small, translucent, and seemingly fragile — approach with confidence. They enter the eel’s open mouth, navigating between teeth designed to grip prey. And they are not harmed. Instead, they remove parasites and dead tissue, providing a service that benefits both species. The eel remains still, almost compliant, in a moment that contradicts everything its appearance suggests. Elsewhere, morays have been observed cooperating with groupers during hunts — a rare example of inter-species coordination among predators. One species flushes prey from crevices; the other intercepts it in open water. These are not random encounters.They are functional relationships — quiet agreements embedded in the fabric of the reef. Predator does not mean solitary. And survival, here, is rarely individual.  The hidden mechanism If there is something truly extraordinary about moray eels, it lies out of sight. Hidden within their throat is a second set of jaws — pharyngeal jaws — capable of moving forward to grasp and pull prey deeper into the esophagus. In the confined spaces where morays hunt, suction feeding — common among many fish — is ineffective. There is no room to generate the necessary force. So evolution took another path. The moray seizes its prey with its outer jaws, then deploys this internal mechanism to complete the capture. A two-step process, precise and efficient, perfectly adapted to life in tight spaces. It is a solution so unusual that it has often been described as alien. But in reality, it is simply the result of constraint — of a body and an environment shaping each other over time.  Beyond fear What we see when we look at a moray eel says as much about us as it does about the animal. We see teeth, and we think danger. We see a hidden body, and we think threat. We see unfamiliar movement, and we assume intent. But the ocean rarely conforms to these projections. The moray eel does not perform for fear. It does not warn, intimidate, or challenge. It exists — within limits defined by structure, oxygen, and opportunity. And when those limits begin to shift — when reefs lose complexity, when interactions break down — the presence of animals like the moray becomes less certain. Not because they are weak. But because they are precise.  Conclusion — Holding the line
In the end, the moray eel is not a symbol of danger, but of balance. A predator that depends on shelter. A solitary hunter engaged in cooperation. A creature feared for behaviors that are often misunderstood. To encounter one is not to face aggression, but to witness a system at work — quiet, efficient, and deeply interconnected. And perhaps the real question is not why we fear them.But why we so often mistake complexity for threat.
Several times a week, I return to the site of Ngouja, in Mayotte.
A simple place, almost still, where time seems to slow beneath the surface. 
There, I find the lagoon’s green turtles.
I watch them graze on the short seagrass with a calm, almost meditative rhythm — like silent herds feeding beneath the water. Their movements are slow, deliberate, repeated — an ancient behavior that seems to belong to a different pace than our own. Beneath them, the seagrass meadows stretch in dense, living patches. They shape the landscape quietly, without ever demanding attention. And yet, as I watch them, another image comes to mind. The Mediterranean. For years, I have moved above the seagrass beds of Posidonia oceanica. A different kind of landscape — denser, more structured, almost forest-like. Where Ngouja feels open and dynamic, Posidonia evokes stability and time. Two environments. Two rhythms. But the same question keeps returning: What do these seagrass ecosystems truly share, beyond their appearance? And what do they reveal about the state of our oceans today? 
Two Worlds, One Function
At first glance, everything seems to separate tropical seagrass meadows from their Mediterranean counterpart. In Ngouja, seagrass is composed of multiple species. It grows quickly, adapts, and recolonizes. Its dynamics are fluid, responsive — but also fragile. In the Mediterranean, Posidonia oceanica follows a different tempo. Endemic to this sea, it expands only a few centimeters per year. Over centuries — sometimes millennia — it builds thick underwater structures known as “matte,” creating one of the most stable coastal ecosystems on Earth. On one side, a fast-growing, adaptive system. On the other, a slow, long-term builder. And yet, despite these differences, their role is the same. Seagrass meadows are among the hidden foundations of coastal oceans. They act as nurseries for countless species, shelter juvenile fish and invertebrates, feed turtles, stabilize sediments, and help maintain water clarity. They also protect coastlines by absorbing wave energy. Without them, entire ecosystems begin to unravel. 
An Invisible Climate Role
But their importance extends far beyond biodiversity. Beneath the surface, seagrass meadows play a critical role in regulating the global climate. They capture carbon dioxide — much like terrestrial forests. But more importantly, they store it. Over time, dead leaves, roots, and organic matter accumulate in the sediment below, forming a long-term carbon reservoir. This carbon can remain trapped for centuries, even millennia. On average, seagrass meadows can store up to 140 tonnes of carbon per hectare. Per unit area, they can be up to 30 to 40 times more efficient than forest soils at storing carbon over the long term. In the Mediterranean alone, Posidonia oceanica captures an estimated 5.7 million tonnes of CO₂ each year. A remarkable figure for such a discreet ecosystem. But this balance is fragile. When seagrass meadows are damaged — by anchoring, pollution, coastal development, or rising temperatures — the carbon they have stored can be released. The system reverses. What was once a carbon sink becomes a source. 
Resilience and Fragility
In Ngouja, tropical seagrass gives the impression of a living, resilient system. Its fast growth allows it to recover under the right conditions. But this apparent resilience comes with vulnerability. Increased turbidity, sediment runoff, or human pressure can lead to rapid decline within just a few years. In contrast, Mediterranean Posidonia tells a different story. It is slow. Extremely slow. But it builds over time. It stabilizes the seabed, stores vast amounts of carbon, and creates long-lasting habitats. When destroyed, recovery can take decades — or may not occur at all on a human timescale. Fast resilience on one side. Deep resilience on the other. Yet in both cases, the same conclusion emerges: These ecosystems are essential and fragile. 
A Silent Decline
Globally, seagrass meadows are in decline. Their disappearance is rarely dramatic. It does not make headlines. It does not burn or collapse suddenly. It happens slowly, underwater, often beyond our awareness. In the Mediterranean, significant losses have already occurred, particularly near urbanized coastlines, ports, and anchoring zones. In the Indian Ocean, data remains limited, making the situation harder to quantify. But pressures are clear: sedimentation, runoff, and coastal development. Less visible than coral reefs, seagrass ecosystems suffer from a lack of recognition. And therefore, a lack of protection. 
Protecting the Invisible
Protecting seagrass does not always require complex solutions. Sometimes, the answers are simple: Limiting uncontrolled anchoring in favor of eco-moorings. Reducing sediment and pollution runoff. Managing coastal development. Strengthening marine protected areas. But all of this depends on one essential step: Recognizing their value. Because it is difficult to protect what remains unseen. 
Conclusion
From Ngouja to the Mediterranean, seagrass meadows tell the same story. That of ecosystems both discreet and essential — capable of sustaining life and regulating the climate, while remaining largely invisible. Two worlds. Two rhythms. One vital function. And perhaps, one shared urgency: To learn how to see what we have long overlooked.
At the surface, the Indian Ocean does not appear different. Waves form, reefs breathe, currents continue their course. Yet within its very structure, something is changing: the salinity of certain regions in the southern Indian Ocean has been measurably and persistently declining for several decades.
A Change Detected Over Decades : This shift is not based on isolated observations. It relies on long-term oceanographic datasets dating back to the 1960s, compiled in the World Ocean Database maintained by NOAA:
https://www.ncei.noaa.gov/products/world-ocean-database These trends have been confirmed and refined by the Argo program, a global network of autonomous floats measuring temperature and salinity throughout the water column since the early 2000s: https://doi.org/10.1016/j.pocean.2009.03.004 Analyses indicate that parts of the southern Indian Ocean show a significant decrease in surface salinity. This signal fits within a broader intensification of the global hydrological cycle under climate change, as highlighted by Durack et al. (2012) in Science: https://www.science.org/doi/10.1126/science.1212222 and reinforced by the latest IPCC assessment (AR6 – Working Group I): https://www.ipcc.ch/report/ar6/wg1/ While global mean ocean salinity remains close to 35 PSU (Practical Salinity Units), that average conceals growing regional contrasts. Subtropical regions dominated by evaporation tend to become saltier, whereas certain tropical zones and parts of the southern Indian Ocean are becoming fresher. This pattern aligns with climate projections indicating that wet regions become wetter and dry regions become drier (IPCC, 2021). 
Why Salinity Is a Fundamental Physical Parameter : Salinity, together with temperature, determines seawater density. Density governs water mass dynamics and drives the global thermohaline circulation, as described by Talley (2013) in Oceanography:
https://doi.org/10.5670/oceanog.2013.07 Cold, salty water is dense and tends to sink, contributing to deep circulation that redistributes heat, nutrients, and oxygen across the planet. Warmer or fresher water is lighter and remains near the surface. If salinity declines, density decreases. Vertical mixing becomes less efficient and stratification intensifies. Stronger stratification limits exchanges between nutrient-rich deep waters and the sunlit surface layer. These exchanges are essential to the functioning of the ocean’s biological pump, a key process regulating carbon uptake and marine productivity, discussed in detail in the IPCC AR6 report: https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-5/ 
Potential Consequences for Marine Ecosystems : The direct biological effects of moderate salinity decline vary by species and region. However, the underlying physical mechanisms are well established. Persistent changes in stratification can influence nutrient availability, alter plankton distribution, and cascade upward through marine food webs.
In the Indian Ocean, where coral reefs and coastal fisheries play major ecological and socio-economic roles, these structural shifts add to existing pressures from warming and acidification (IPCC, 2021). They represent a gradual reconfiguration — less visible than coral bleaching events, but potentially just as consequential over time. 
A Marker of an Intensifying : Water CycleSurface salinity is now recognized as a robust tracer of hydrological cycle intensification. A warmer atmosphere can hold more water vapor, modifying precipitation patterns and increasing regional contrasts (IPCC, 2021).
In the case of the Indian Ocean, the observed freshening reflects a progressive reorganization of the system. It is not immediately visible to the naked eye, but it influences water mass stability, regional circulation, and potentially atmosphere–ocean interactions, including those that contribute to monsoon dynamics. 
A Climate Paradox — Freshening in a Warming : World At first glance, the idea that parts of the Indian Ocean are “freshening” may sound contradictory in the context of global warming. But freshening does not mean cooling. It refers to a decline in salinity, not temperature. In fact, ocean warming and surface freshening are often linked through the same mechanism: an intensified hydrological cycle.
As the atmosphere warms, it holds more moisture, leading to stronger rainfall in some regions and enhanced evaporation in others. Where precipitation and freshwater inputs increase, surface waters become less saline even as they continue to warm. The result is not a cooler ocean, but a more stratified one — warmer at the surface, fresher at the top, and increasingly layered. This apparent paradox illustrates how climate change does not produce uniform responses, but rather a complex reorganization of ocean structure. 
Why the Ocean Is Salty — And Why That Matters : To understand why these variations are significant, it is useful to revisit a fundamental question: why is the ocean salty? Ocean salinity results from a dynamic balance established over millions of years. Rainwater dissolves minerals from continental rocks. Rivers transport dissolved ions to the sea. Submarine hydrothermal systems add additional chemical elements. When seawater evaporates, the water leaves but the salts remain. This cycle, explained by NOAA: https://oceanservice.noaa.gov/facts/whysalty.html has maintained a relatively stable global salt balance on geological timescales. A rapid regional shift in salinity does not mean the ocean is “losing its salt” globally. Rather, it indicates that the distribution of freshwater is changing enough to alter the physical structure of the water column. 
A Silent but Structural Transformation : Public discussions about ocean change often focus on rising temperatures or acidification. Yet salinity reveals a complementary and essential dimension: how accumulated energy in the climate system redistributes freshwater and reshapes ocean structure.
If temperature tells us how much the ocean is warming, salinity tells us how it is reorganizing. Beneath the apparently unchanged surface of the Indian Ocean, this transformation is already measurable. It is gradual, physically consistent with climate projections, and potentially decisive for marine ecosystems and circulation patterns in the decades ahead. From the Heart of Voh to the essence of mangroves Mangroves protect coastlines, store carbon and sustain life — yet they are vanishing. From the Heart of Voh to the shores of Mayotte, this is the story of a fragile ecosystem at a turning point.  I first discovered the power of mangroves not by walking through the mud, but through an image: Yann Arthus-Bertrand’s aerial photograph of the Heart of Voh in New Caledonia. Seen from above, this improbable shape draws a heart within the mangrove forest. To me, it captures what mangroves truly are: a quiet, often overlooked ecosystem — yet vital, a coastal heart beating for the planet. Mangroves are tropical and subtropical forests growing in the intertidal zone, where saltwater, freshwater and land meet with the rhythm of the tides. They are made of highly specialized trees and shrubs — mangrove species — able to survive extreme salinity and flooding. Globally, scientists recognize around 70 true mangrove species, spread across the coasts of more than 120 countries. But to describe mangroves as “just forests” is misleading. They are a keystone ecosystem, a biological crossroads where water, carbon, nutrients and marine life cycles converge.  What a mangrove does — an ecosystem working for usA mangrove is not a line of trees along the shore. It is a living system, constantly active above and below the surface, helping coastal environments remain in balance. In its waterlogged, oxygen-poor soils, mangroves lock away vast amounts of carbon. This carbon — captured from atmospheric CO₂ — can remain stored for decades or even centuries. For us, the meaning is simple: as long as this carbon stays buried, it does not fuel climate change. When a mangrove is destroyed, that stored carbon can be released, adding to the greenhouse effect. Facing the sea, mangroves act as a natural buffer. Their tangled roots slow waves, trap sediments and stabilize shorelines. Where mangroves remain, they reduce erosion, dampen storm surges and protect coastal communities from increasingly violent weather. (UNEP overview: https://www.unep.org/explore-topics/oceans-seas/what-we-do/protecting-restoring-blue-carbon-ecosystems) Below the surface, mangroves are a giant nursery. Thousands of organisms find shelter here: fish larvae, juvenile sharks, crustaceans, mollusks, birds and reptiles. For many species, this is their first refuge before reaching the open sea — a growth space that later sustains reefs and fisheries (FAO module: https://www.fao.org/sustainable-forest-management-toolbox/modules/mangrove-ecosystem-restoration-and-management/en). They also play a quiet but essential role in water purification by trapping sediments and filtering nutrients, helping protect nearby ecosystems such as seagrass meadows and coral reefs. For all these reasons, mangroves cannot be treated as scenery. They are a natural infrastructure, silent yet indispensable.  Major losses… and a fragile recoveryFor decades, mangroves have been cleared, fragmented and transformed — often out of sight. Aquaculture, agriculture, urban expansion and infrastructure have steadily eaten away at these amphibious forests. With the satellite era, monitoring has become far more precise. The global reference today is Global Mangrove Watch. According to this dataset, between 1996 and 2020 the world lost 5,245 km² of mangroves, about 3.4% of the global total (Source: Bunting et al., 2022, Remote Sensing; platform update via Wetlands International: https://www.wetlands.org/global-mangrove-watch-platform-updated-with-the-latest-data-to-2020/). That is nearly the size of the U.S. state of Delaware — an entire living coastline erased in a single generation. Data from the FAO (Food and Agriculture Organization of the United Nations) confirm this trend: the rate of loss has slowed since the 2000s, but it has not stopped (FAO global assessment 2000–2020: https://openknowledge.fao.org/server/api/core/bitstreams/7f15adf1-2756-4e86-a6dd-77d0fc26d97c/content).  The Women of the Mangrove. The Mamas Shingos of MayotteIn Mayotte, along the edges of the lagoon, groups of women known as the mamas Shingos still harvest shellfish and small marine life in the mangrove at low tide. Their movements follow the same rhythm as the tides, passed from generation to generation. They also collect seawater and let it slowly evaporate in shallow basins under the sun, leaving behind coarse crystals of salt. It is a quiet process, shaped by patience and heat — a transformation of the sea itself into something that can be shared, traded, and preserved. For them, the mangrove is not a concept. It is food, income, knowledge, and identity. When the mangrove recedes, it is not only an ecosystem that disappears, it is a way of living, a fragile balance between survival and nature. Their presence reminds us of something essential: protecting mangroves is not only about carbon or coastlines. It is about dignity, continuity, and the right to remain connected to the living world.  Blue carbon: a real promise — but not a magic solution“Blue carbon” is now a central argument for protecting mangroves — and rightly so. They store enormous amounts of carbon, especially in their soils. When a mangrove is destroyed, this carbon can be released into the atmosphere, worsening climate change. Globally, mangroves store around 6.4 billion tonnes of carbon in their biomass and soils equivalent to more than 23 billion tonnes of CO₂. That is roughly equal to over five years of total European Union emissions. But reality is more complex. Mangrove soils can also emit other greenhouse gases, such as methane (CH₄) and nitrous oxide (N₂O) — far more powerful than CO₂. Depending on local conditions, these emissions can reduce part of the net climate benefit (Rosentreter et al., 2021: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020GB006858). This does not mean mangroves are “bad” for the climate. It means their impact depends on the site, the ecosystem’s health, and how it is protected or restored. The key message is this: mangroves are a powerful climate ally, but they cannot be reduced to a single carbon number. Protecting the whole ecosystem matters more than counting tonnes of CO₂.  False good solutionsThe first trap is to confuse planting with restoring. Planting mangroves without restoring water flows, tides and sediments often leads to failure. The result may look reassuring — but the ecosystem does not function. Another risk is turning blue carbon into a communication tool, where the credit becomes the goal rather than the ecosystem itself : https://mangroveactionproject.org/wp-content/uploads/2024/07/SOWM-2024-HR.pdf). A necessary shiftThese mistakes do not come from bad intentions, but from a misunderstood urgency. Faced with collapse, we wanted quick, visible action. But science now shows that mangroves cannot be rebuilt like a park. They are shaped by water, tides, sediments and time. By confusing speed with effectiveness, we sometimes created the illusion of rescue. This shift in understanding marks a turning point: to protect is not to replace — it is to allow life to continue.  Real solutionsThe most effective solution is still the simplest: protect the mangroves that remain. Every hectare preserved avoids emissions, shields coasts and sustains nurseries. When restoration is necessary, it must start by restoring natural hydrology, then letting regeneration do its work. It is slower — but infinitely more durable.  Conclusion :
So the heart can keep beatingThe Heart of Voh is not just a famous photograph. It is a fragile symbol, suspended in time. Nothing guarantees it will still be visible tomorrow — or that other mangroves will have the chance to trace, by chance, what we recognize as a heart. Protecting mangroves is not about saving a distant landscape. It is about preserving a vital function of the planet — a discreet but essential organ, without which our coasts, oceans and climate become more unstable. If we want future generations to still glimpse a heart beating from the sky — in Voh or elsewhere then mangroves must no longer be a backdrop we watch disappear, but a living system we choose to protect. Because in protecting mangroves, we are not only defending the shoreline We are protecting the very heart of our world.  Some days change something. Not because of a spectacular event or a scientific breakthrough, but because you can feel it — quietly — a new relationship with the ocean taking shape. Today was one of those days. It began with a simple question on the boat, as it often does. One of the young divers asked me how many sharks are killed every year. When I answered 70 to 100 million, the whole group fell silent. Then came the second question: “But… why?” And that’s when everything started moving: industrial fishing, finning, the disappearance of a predator the ocean desperately needs. Then we talked about the role of turtles in Mayotte -- the gardeners of the lagoon — cleaning seagrass, redistributing nutrients, maintaining a fragile balance very few people know about. These simple exchanges are where sparks begin.  The “Naimi Effect”And then there’s Naimi. When she joined the program, she was preparing for her math–physics baccalauréat, bright, focused, heading toward the classic science path. But dive after dive, something shifted. She started asking different questions. Not just “how does this work?” but “could I work in this field one day?” Today, she says out loud what she barely dared to think a few months ago: she’s considering marine biology. That’s not a small turn — it’s a whole life pivoting, quietly, shaped by experiences underwater, by encounters, by understanding. When a 17-year-old begins to look at the ocean not as a backdrop but as a possible future, it means something real is happening.  Diving Is No Longer a Hobby — It’s a Doorway. The questions are changing. In the beginning they asked: “Is it deep? How long will we stay? What fish is that?” Now it’s becoming:
from experience to vocation. It’s exactly what I hoped for — quietly, secretly that diving wouldn’t just be an activity, but a gateway to a deeper understanding of their island, their lagoon, their future.  A New Relationship with the OceanSharks, turtles, seagrass, reefs… These are no longer abstract words. They’re things they’ve seen, felt, understood, protected. A new relationship with the ocean is taking root. Not through big speeches -- but through accumulated experience:
 And Me, in the Middle of All ThisI watch them evolve, grow, open up.
This isn’t just a project. It’s a transformation. Each time a young diver tells me, “I’d like to work in the ocean too,” I feel that all the hours teaching, filming, reassuring, guiding… they all land somewhere meaningful. The Ambassadeurs du Lagon are no longer teenagers learning to dive. They are slowly becoming the Sentinelles du Lagon -- the future guardians of a world they’re only beginning to understand. And that might be the most beautiful thing I’ll have witnessed here. How do marine animals reproduce underwater?Underwater reproduction varies greatly across species. Sharks reproduce through internal fertilization, using specialized structures called claspers to transfer sperm directly to the female. Many reef fish, like clownfish and wrasses, spawn externally by releasing eggs and sperm into the water. Some species can even switch sex during their lifetime — a process known as protandry or protogyny — to maximize reproductive success under changing social conditions. 
In our imagination, animal reproduction follows simple rules: a male, a female, and the continuation of the species. But in the Indian Ocean and beyond, life has developed strategies that overturn these certainties. Some species can change sex depending on their position in the social hierarchy. Others, in the total absence of a male, can give birth entirely on their own. These stories, which sound like science fiction, are in fact very real.
The Clownfish: A World Ruled by FemalesPopularized by the movie Finding Nemo, the clownfish has become one of the most famous ambassadors of the underwater world. Yet the film deliberately ignored a striking biological truth: in every anemone, it is a female that reigns supreme.
Their society is strictly hierarchical. The largest fish is the dominant female. Next comes a smaller breeding male, followed by a series of immature males waiting their turn. If the female dies, the breeding male changes sex and becomes female. One of the immature males then rises to take the vacant breeding role. This phenomenon, called protandry, makes clownfish champions of biological flexibility. It ensures the colony’s survival — no group is ever left without a female. But it also challenges our notion of what is “natural.” Here, nature doesn’t freeze roles; it adapts them to the ecosystem’s needs. 
Do sharks have sex?Yes — sharks reproduce via internal fertilization. Male sharks use paired organs called claspers, extensions of the pelvic fins, to deliver sperm into the female’s body. This ensures fertilization takes place internally, which is crucial given that water currents would otherwise disperse eggs and sperm quickly in the open ocean. After fertilization, shark species vary: some lay eggs in protective capsules (oviparity), while others retain the embryos and give birth to live young (viviparity). Why do some fish change sex?Many reef fish are sequential hermaphrodites — they can change sex during their lifetime depending on social structures or reproductive advantage.
This adaptation allows species to maintain viable mating populations even when the balance of males and females shifts over time. Protandry → male to female
Sharks: Giving Birth Without a PartnerIf clownfish are masters of flexibility, sharks push the limits of biological imagination even further. In several aquariums around the world, biologists have observed female sharks giving birth despite the complete absence of a male.
The first documented case dates back to 2001, with a bonnethead shark (Sphyrna tiburo). Since then, the phenomenon has been confirmed in other species: the zebra shark (Stegostoma tigrinum) and the leopard shark (Triakis semifasciata). DNA testing revealed that the offspring were indeed produced by a single female, without any male contribution. The mechanism is known as parthenogenesis. In simple terms, the egg fuses with a polar body — a by-product of cell division during meiosis. The result is a viable embryo, but with reduced genetic diversity: the pup inherits only maternal DNA. This form of “virgin birth” is not a miracle solution. It allows a solitary female to pass on her genes, but it does not guarantee the long-term survival of a species. A population that reproduces exclusively through parthenogenesis would quickly face the risks of inbreeding. 
When Biology Outruns FictionThese phenomena may seem anecdotal, but they reveal much about life’s creativity. Marine biology is not locked into binary patterns; it is constantly experimenting, adapting, and reinventing.
For clownfish, sex change is a safeguard for colony survival. For sharks, parthenogenesis is an emergency fallback when no mates are available. Both strategies showcase extraordinary resilience. Yet they also reveal the limits of that resilience. In today’s ocean — disrupted by climate change, overfishing, and habitat destruction — such mechanisms are not enough to save threatened species. They are biological stopgaps, not permanent solutions. 
Lessons for UsWhat can we take from these stories, beyond their fascination?
First, they remind us that nature is infinitely more inventive than our cultural models. The notions of “male” and “female,” fixed in our minds, are in fact variables in the ocean — roles adapted to circumstances. Second, they show that the survival of a species does not depend only on extraordinary biological tricks. It depends above all on the environment in which the species lives. A clownfish can change sex, a shark can give birth without a mate — but if their reefs vanish, if their oceans are emptied of fish, no adaptation will be enough. Finally, they push us to reflect on our role. Observing these biological marvels should inspire awe, but also responsibility. Protecting habitats, limiting human pressure — that’s what gives these species the chance to display the full ingenuity of life. 
Clownfish and sharks teach us a paradoxical lesson: nature can reinvent itself, but it is not invincible. Each strategy has its limits.
In a world where the ocean is changing at unprecedented speed, it is not enough to marvel at curiosities of biology. We must protect the conditions that allow them to exist. Because behind every camouflage, behind every fatherless birth, lies a simple truth: without a healthy ocean, even the miracles of biology fade away. FAQ – Clownfish Sex Change & Shark ReproductionQ1.How long does it take for a male clownfish to change sex?Behavioral change occurs within 1–3 days after the dominant female disappears. Gonads become functional female organs in 2–3 weeks, and full fertility is usually reached in 4–8 weeks. Q2.How many marine species can change sex? Examples?More than 500 fish species (≈2% of teleosts) can change sex:
Q3.Does sex change occur on land in the animal kingdom?Among terrestrial vertebrates, social sex change like in clownfish is extremely rare. However:
In mammals and birds, sex change does not occur naturally. Q4.How long does it take for a female shark to lay eggs or give birth?Oviparous sharks (e.g. catsharks, zebra sharks): lay 1–2 egg cases every 1–3 weeks during the season; incubation lasts 3–6 months (sometimes up to 12). Viviparous/ovoviviparous sharks (e.g. hammerheads, lemon sharks): pregnancy lasts 10–12 months, and in some species up to 18–24 months.
What is dolphin skin made of?
Dolphin skin is made of a highly elastic outer epidermis combined with a dense, collagen-rich dermis underneath. This structure allows the surface of the skin to deform microscopically as water flows across it, absorbing turbulence instead of letting it build up. Unlike most animals, dolphins continuously renew their outer skin layer, which helps keep the surface extremely smooth and free from parasites, algae, and drag-inducing roughness. This unique combination of elasticity, rapid regeneration, and micro-scale surface control is one of the key reasons dolphins can swim at high speeds with remarkably low resistance. 
In the mysterious depths of the ocean, every species has had to adapt to the relentless laws of physics to survive. Among the champions of hydrodynamics, dolphins and sharks dominate the waters, reaching impressive speeds and navigating with an ease that defies comprehension. Behind their performance lies an evolutionary secret: the structure of their skin.
Dolphin skin under magnification — The smooth, elastic surface of dolphin skin helps dampen turbulence and maintain a stable flow of water along the body, reducing drag and improving swimming efficiency.
The Dolphin's Secret: Intelligent Skin
Dolphins, true acrobats of the ocean, can slice through the water at speeds exceeding 50 km/h (31 mph). The common dolphin (Delphinus delphis), for example, is known for its bursts of speed and ability to surf the waves. Its secret lies partly in the dynamic structure of its skin. Composed of an elastic outer layer and a deeper layer of collagen, their skin absorbs and dampens water turbulence. This phenomenon, known as drag reduction, allows them to minimize resistance and conserve energy. Studies have shown that dolphin skin contains microscopic folds that adjust according to hydrodynamic forces, reducing vortices that would otherwise slow them down. Some researchers are now drawing inspiration from this structure to design anti-friction materials for the naval and aerospace industries. One notable example is the development of dolphin-inspired coatings for submarines and ships. Engineers have tested flexible hull materials that mimic dolphin skin’s ability to adjust to water pressure, leading to reduced fuel consumption and increased speed. This technology could revolutionize underwater transportation by making vessels more energy-efficient and maneuverable. 
The Living Armor of Sharks
While dolphin skin is flexible and dynamic, shark skin is a true microscopic armor. Covered in tiny dermal denticles—small rigid structures similar to serrated scales—it plays a crucial role in their speed and maneuverability. The great white shark (Carcharodon carcharias), for example, can reach speeds of up to 56 km/h (35 mph) thanks to this adaptation. The dermal denticles create a textured surface that channels water into fine layers, reducing drag and increasing swimming efficiency. This unique coating also limits the growth of algae and parasites, an evolutionary advantage that allows sharks to maintain optimal hydrodynamics without being slowed down by unwanted organisms. Inspired by this adaptation, engineers have developed biomimetic coatings for ship hulls and swimsuits. In fact, some shark-skin-inspired swimsuits were banned from the Olympic Games after it was proven that they provided swimmers with an unfair advantage.
Why dolphin skin is so hydrodynamically efficientWater flowing over a dolphin’s body does not behave like it does over a rigid surface.
Because the skin is soft and elastic, it can subtly adapt to changes in pressure and flow, reducing the formation of turbulent vortices that normally slow an object down in water. This effect is known as turbulence damping. Instead of breaking the flow into chaotic swirls, dolphin skin helps maintain a smoother boundary layer, allowing water to slide along the body with minimal energy loss. This is why dolphins can cruise efficiently for long distances and still reach explosive bursts of speed when hunting or escaping. 
Shark skin vs dolphin skin — two different solutions to the same problemAlthough dolphins and sharks both move with extraordinary efficiency through water, their skins solve the problem in completely different ways.
Shark skin is covered with millions of microscopic tooth-like structures called dermal denticles. These tiny ridges channel water into narrow streams, reducing drag and preventing turbulent flow from forming. This system is so effective that it has inspired modern aircraft coatings, swimsuits, and boat hulls through biomimicry. Dolphin skin, on the other hand, does not rely on hard structures. Instead, it uses soft, deformable tissue to smooth out water movement dynamically. One species uses micro-armor to guide the flow. The other uses elasticity to absorb it. Two evolutionary paths — same hydrodynamic goal. 
Why Can't Humans Compete?
Unlike dolphins and sharks, the human body is not designed for optimal hydrodynamics. Our smooth skin creates more friction with water, and our muscles are not optimized for efficient propulsion in this element. Even with cutting-edge equipment, we remain far from the natural efficiency of these marine predators. 
Sharkskin: The Banned Technology
In the 2000s, sports equipment manufacturers designed swimsuits inspired by shark skin, called sharkskin suits. These suits were covered with micro-relief structures mimicking the dermal denticles of sharks, reducing drag and improving buoyancy. They allowed swimmers to shave off crucial fractions of a second in competition. Their effectiveness was so remarkable that at the 2008 Beijing Olympics, over 90% of medalists wore these suits, breaking numerous world records. In response to this disparity, the International Swimming Federation (FINA) decided to ban these swimsuits in 2010, arguing that they provided an artificial advantage beyond the athletes' natural abilities. However, while based on the concept of shark denticles, these suits did not perfectly replicate the complex structure of real shark skin. Shark skin functions not only through its texture but also through the flexibility and dynamics of its denticles, which adapt to water flow. Despite its biomimetic inspiration, sharkskin technology remained an approximation of nature's perfection. 
Two Strategies, One Goal
Dolphins and sharks have taken different evolutionary paths to achieve the same result: fluid and efficient navigation. While dolphin skin adapts in real time to turbulence, shark skin stiffens and channels water flow. Two fascinating biomechanical solutions that highlight nature's ingenuity. In laboratories worldwide, these natural marvels are inspiring innovations in fields ranging from maritime transport to sports equipment. Prototypes of dolphin-inspired submarines are being developed, and biomimetic underwater drones based on shark skin could one day revolutionize ocean exploration. Once again, the ocean proves to be an infinite reservoir of solutions for the future. And beyond dolphins and sharks, other marine creatures hold secrets of hydrodynamic perfection. From the streamlined bodies of orcas to the undulating propulsion of cuttlefish, the ocean continues to challenge our understanding and inspire the next wave of human innovation. Frequently asked questionsWhat does dolphin skin feel like?
Dolphin skin feels smooth and firm, with a rubber-like elasticity that allows it to flex under pressure from moving water.
Why is dolphin skin so smooth?
Dolphins continuously renew the outer layer of their skin, which helps prevent algae, parasites, and roughness from building up.
How does shark skin reduce drag?
Shark skin is covered with microscopic dermal denticles that create tiny channels in the water flow, helping reduce turbulence and drag.
Can humans copy dolphin or shark skin?
Yes. Both dolphin-skin-inspired elasticity and shark-skin-inspired micro-textures have influenced biomimetic designs for surfaces built to reduce drag.
Read More : The business of Sharks
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Serge Melesan
Underwater & Fine Art Ocean Photographer Specialist in Fine Art Ocean Photography. Published in Oceanographic Magazine & Earth.org. National Geographic Traveller – Portfolio Winner (2023). Archives
Mai 2026
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