Preserving Con Dao’s Coral Reefs: [1] Treasure beneath the waves

Forests beneath the sea

In early 2024, I embarked on my first field trip to Con Dao. Throughout the journey, Mr. Nguyen Khac Pho, Director of the Con Dao National Park Management Board, introduced me to the island's unique treasures, a rare, highly rich biodiversity system stretching from primary tropical forests on land to vibrant coral reefs beneath the waves.

By April, the northeast monsoon fades away, leaving the seas calm and gentle. This makes the waters of Dam Tre Bay - sheltered snugly between ancient primary forests across Con Dao's 16-island archipelago - as smooth and transparent as a giant mirror.

According to data compiled by Con Dao National Park, the area boasts approximately 1.800 hectares of coral reefs, housing 360 species across 61 genera and 17 families. This makes it one of the most biodiverse coral ecosystems in Viet Nam, serving as a critical sanctuary, breeding ground, and nursery for thousands of marine species.

According to data compiled by Con Dao National Park, the area boasts approximately 1.800 hectares of coral reefs, housing 360 species across 61 genera and 17 families. This makes it one of the most biodiverse coral ecosystems in Viet Nam, serving as a critical sanctuary, breeding ground, and nursery for thousands of marine species.

From the speedboat, the aquamarine water is clear enough to reveal glimpses of coral formations undulating under the seabed. However, the true transformation occurs only after donning a diving mask and following Con Dao’s forest director a few meters below the surface.

Beneath the waves of Dam Tre Bay, the ocean floor unfolds like a vibrant canvas. Table corals stack like colossal umbrellas, while branching corals stretch upward like miniature trees swaying to the rhythm of the currents.

Darting through these underwater forests are schools of butterflyfish, parrotfish, damselfish, and clownfish. In deeper rocky crevices, giant clams lie silently, living testaments to the untouched, pristine nature of this protected marine environment.

The bay is a premier destination for both domestic and international travelers. During our dive, groups of foreign tourists could be seen adjusting their masks and snorkels before disappearing beneath the blue surface, resurfacing minutes later with enthusiastic thumbs-up signs and smiles, proving that language is unnecessary when facing the beauty of Con Dao's coral world.

"To truly understand Con Dao, you cannot just look at the sea from the shore; you must submerge to the ocean floor. Corals are the very foundation of this entire ecosystem," Mr. Pho smiled after surfacing.

Just as primary forests preserve the green canopy of the islands, these coral reefs function as "oceanic forests." They nourish thousands of marine organisms, offering breeding habitats that sustain the wider Con Dao maritime region. Mr. Pho pointed toward a massive table coral patch nearly the size of a woven mat, where green damselfish and yellow butterflyfish darted into crevices.

"They look stunning, but every single coral cluster here takes decades, even centuries, to fully develop," Mr. Pho added.

The Con Dao marine ecosystem relies on a vital interconnectedness among coral reefs, seagrass beds, and mangrove forests. The coral reefs act as spawning grounds for fish, seagrass beds serve as natural nurseries for larvae, and mangroves shield juvenile species before they grow and return to the open ocean. This ecological chain infuses life into the entire region.

Local and visiting fishers alike understand this delicate balance. Repairing his nets near the Ben Dam wharf, Mr. Nguyen Van An, a veteran fisherman with over three decades of seafairs around Con Dao, shared that local mariners have long revered coral reefs as the structural roots of the sea.

Leaving Dam Tre Bay at midday, I looked back at the placid water, still captivated by the bustling "metropolis" thriving just a few meters beneath the quiet surface.

Safeguarding green wealth for the next generations

Our survey alongside Con Dao National Park specialists continued across multiple sites: Hon Ba, Hon Tre Lon, Ong Dung Beach, Ong Cuong Beach, Hon Cau, and Hon Bay Canh.

Each site revealed a unique coral morphology. In some zones, table corals carpeted the seabed like sprawling fields; in others, dense thickets of staghorn corals offered refuge to schools of small fish. Elsewhere, massive boulder corals sat like ancient sentinels that had weathered centuries of oceanic shifts.

At each stop, the rangers patiently identified distinctive species. There were delicate, fast-growing Acropora branches, slow-growing Porites blocks that take decades to expand by just a few centimeters, and uniquely shaped Pachyseris, Montipora, and Pavona colonies. While an untrained eye might see mere rocks, conservationists read these corals as vital medical charts indicating the health of the ocean.

However, like reef systems globally, Con Dao's underwater forests face growing pressures from climate change and anthropogenic impacts. Conservation experts note that while coral reefs cover less than 1% of the ocean floor, they shelter roughly 25% of all marine life. These fragile structures also act as natural breakwaters, absorbing the energy of massive waves before they crash into the island shores. If these critical ecological links are broken, the entire coastal ecosystem suffers.

According to Dr. Vo Si Tuan, former Director of the Institute of Oceanography, corals are the literal foundations of coastal ecosystems. When reefs are healthy, fish stocks regenerate, biodiversity remains stable, and marine economic activities, ranging from regulated fisheries to ecotourism, can thrive sustainably.

Recognizing this immense value, Con Dao National Park’s marine rangers maintain a relentless patrol schedule. Between 2021 and 2025, teams executed thousands of marine patrols, successfully detecting and handling unauthorized intrusions into strictly protected waters.

Yet, as Mr. Pho emphasized, enforcement alone is insufficient. The ultimate victory in conservation lies in public awareness. Sustainable preservation is only achieved when fishermen view corals as the "home of the fish" and tourists treat the ocean floor with respect.