Protection came in stages. Parts of the archipelago were given reserve status in 1984, the national park itself was created by Decision 135/QĐ-TTg on 31 March 1993, and the boundaries were extended again in 1998. The shape of the result is unusual for Vietnam. Of 19,883 hectares under protection, only 5,883 are land — forest covering most of the sixteen islands — while 14,000 hectares are sea. Beyond that lies a marine buffer zone of 20,500 hectares, which means the cushion around the park is larger than the park. Almost all of it is managed as no-take water. That single decision, more than any species programme, is why the reefs here still look the way reefs are supposed to look.

Surveys have recorded 1,077 vascular plant species on the islands and 155 land vertebrates among them — 25 mammals, 85 birds, 32 reptiles and 13 amphibians. In the water the count runs to roughly 1,725 marine organisms, including 360 species of coral, 205 reef fish, eleven seagrasses and seven marine mammals; 37 seabird species use the cliffs and islets. Two of the land animals belong nowhere else. The crab-eating macaques that patrol the path down to Ông Đụng beach are a subspecies endemic to Côn Đảo, and so is the black giant squirrel, a spectacular dark animal with a tail longer than its body that most visitors hear before they see. Anyone who has snorkelled elsewhere in Vietnam notices the difference within about ninety seconds of putting a mask in the water.

The park's rarest resident is also its least cooperative. Dugongs graze the seagrass meadows here, and they are the reason those eleven seagrass species matter as much as the coral does — a dugong is essentially a large mammal that has committed entirely to eating underwater grass, and where the meadows go, it goes. Sightings are infrequent enough that most park staff can date theirs. The same shallows support hawksbill and green sea turtles, both endangered, and dolphins pass through regularly. What makes Côn Đảo unusual is that mangrove, seagrass meadow and coral reef all occur inside one protected boundary, which is exactly the combination that lets a marine system rebuild itself: the mangroves hold the sediment, the seagrass feeds the grazers and shelters the juveniles, the reef does the rest.

On paper the record is excellent. The park was listed as a Wetland of International Importance under the Ramsar Convention in 2013, as site number 2203, and named an ASEAN Heritage Park in 2023. As far back as 2006 a UNESCO delegation surveyed the islands and concluded they would qualify as a mixed natural and cultural World Heritage Site, given that the prison camps and the ecosystems occupy the same ground; twenty years on, the nomination has still not been inscribed. On the ground the record is messier. A paved road through sensitive terrain was proposed by local government, opposed by conservationists, and rejected at national level — and then, in 2017, construction started anyway. Small islands with growing tourist economies generate this argument continuously, and the designations do not settle it.

The park is not difficult to enter, which is part of its appeal. A ticket office sits up the hill out of Côn Sơn town, directly across the road from the ruins of the Ma Thiên Lãnh bridge, which prisoners died building — the conservation area and the penal colony share a boundary and, in places, the same stones. From there a short stone path climbs to the Hang Đức Mẹ grotto, and another drops through forest to Ông Đụng beach, small and rocky and usually empty. The stiff walk up to Sở Rẫy ends at an abandoned plantation and an observation tower with the island's best view. Only the long route to Đầm Tre, the far northern bay, needs a guide and attention to the tides. One local caution is worth taking seriously: at the island's southern tip near Nhất beach, wind can arrive without warning and with enough force to knock a person down.