BUNAKEN NATIONAL PARK, INDONESIA — In the 1950s, Alfred Hitchcock made a thriller called Rope, starring Jimmy Stewart. The title was a double entendre; not only was a rope involved in the crime, but Hitchcock made it appear that the whole film was shot in a single, unspliced, 80-minute take.

In the bath-warm waters of Bunaken Island, a dive is also about 80 minutes long; twice the length of a dive in colder, deeper water. From the moment I roll off the boat to the instant I surface — a single “take,” defined by the amount of compressed air in my tank — it’s as if I’m immersed in a conceptual film; a seamless drama with intricate subplots, set on an impossibly alien world. Blue ribbon eels unfurl their fluorescent bodies into the current; decorator crabs prance across the coral heads wearing live anemones on their backs; ornate ghost pipefish hang above soft corals like feathered seahorses.

I pass a shallow cave, waking a loggerhead turtle, and watch the giant creature knife toward deeper waters with the grace of a slow-moving pelican. Below, a white-tipped shark slices through a school of snapper. There are dull moments and moments of drama, slices of life, celebrity encounters with rare and spectacular fish. No popcorn, unfortunately, and the soundtrack is a bit monotonous — the magnified gurgle of my own bubbles — but the casting and set design are terrific. I’d give this film two thumbs up — but the same cut never plays twice.

Bunaken was one of Indonesia’s first marine parks, created in October, 1991. Seven years later, marine biologist Mark Erdmann, along with local activist Meity Mongdong and divemaster Christiane Muller, helped create a management board for the national park. They managed to shift control of the park away from the central government (in Jakarta), and put it in the hands of local villagers, fishermen, and dive operators — people with a vested interest in preserving the area’s ecology.

Coral reefs are often called the “rainforests of the sea,” and there aren’t as many of them as you might think. If you took all the world’s reefs and put them together, they’d cover an area only half the size of France. At present, they are so endangered that 70% of them will cease to be viable within 50 years.

Unfortunately, the years prior to 1991 saw a lot of bad mojo at work around Bunaken’s reefs and mangrove swamps. The reefs around at least three of the islands — Bunaken, Manado Tua and Nain — were fished with bombs and cyanide. Low tides forced local boats to anchor amid the fragile corals, and dive boats (not to mention clumsy divers) wrought havoc as well. Storms reduced already weakened corals to rubble. By the time the national park was created, big sections of the reef were already in dire shape.

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This particular area of Northern Indonesia, where Alfred Russel Wallace got the jump on Darwin in 1859, is considered one of the most spectacular dive sites in the world. There are a couple of reasons for the area’s astonishing beauty. The first is that the islands are surrounded by a huge submarine trench, nearly three miles deep at places. Diving along the wall is dizzying; it’s like hovering in space, just over the edge of the Grand Canyon.

The trench is a blessing. Cool water welling up from the depths helps protect the reef against global warming, and makes the area a perfect environment for everything from featherworms to spinner dolphins.

The second reason divers love this area is the fact that the Pacific Ocean (to the northeast) is a foot higher than the Indian Ocean (to the southwest). This creates an immense current called the Indonesian Throughflow, which swirls and dips around Sulawesi’s coastline, islands, and trenches. Sea creatures of all sizes are carried into these waters, a biologist’s wet dream. A new species of seahorse was discovered as recently as 1993, by a local divemaster named Henche Pontoh; the creature, Hippocampus pontohi, bears his name.

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Let’s say you want to revive a crippled reef. There are various strategies you can use, from sinking old railroad cars to dropping huge cement balls into the rubble; anything to give new corals a handhold. But the most elegant fix may well be EcoReefs: white ceramic modules, the size of squat, round coffee tables, that look like 3-D snowflakes (they’re inspired by the shape of staghorn coral). Anchor enough of them in the rubble, the theory goes, and a new reef will take root on their welcoming arms.

EcoReefs are the brainchild of Michael Moore, who lives in San Francisco. Moore looks a bit like the young Ed Harris, and holds a Ph.D. in integrative biology from UC Berkeley.

A couple of years ago Moore shot some underwater footage, documenting a year-long test of his ceramic modules here in Bunaken. Within a few months the EcoReefs had attracted large populations of fish, who used the branching arms of the structures for shelter. Within a year, tiny polyps — the animals that actually create coral reefs — had begun to settle on the modules’ arms as well.

I’ve come to Bunaken to check out two Seacology projects — both of which funded the installation of EcoReefs — and observe their progress first-hand.

The largest is off the coast of Manado Tua, a perfectly round island just northwest of Bunaken, dominated by the towering cone of a dormant volcano. The blasted reefs outside of Nigiri village were shored up with 620 modules, given in exchange for an agreement to leave the area alone: No Fishin’. There’s no diving, either — but exceptions are made for biologists and, fortunately, journalists.

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Froggies Divers sits on the curving southern shore of Bunaken’s hourglass-shaped coastline, a funky resort of clapboard bungalows with thatched roofs, a sand-floored dining area (with good Minahasan food), and a lively, expressive population of geckos. The owner and proprietor is Christiane Muller, 67. She’s as unusual a creature as you’re likely to find on Sulawesi’s reefs. Christiane had numerous previous lives before Froggies, working as a DNA researcher, a simultaneous translator (she speaks six languages), and as a field recorder of Southeast Asian music.

“I’d never had any interest to dive,” she says, lighting another in an endless series of clove cigarettes. “But in 1988, I was on vacation in with my son, Martin, in the Carribbean. He was going scuba diving, and asked me to join him. I said no, and he said, ‘I dare you.’ That was all it took.”

Two years later, Christiane was a divemaster; a year after that, she opened Froggies.

Christiane and I anchor to a mooring in sight of the village of Nigiri, where the red spires of Manado Tua’s white church rise into the shimmering sky. We strap on air tanks, roll backwards into the water, and begin our descent.

The EcoReefs cover several thousand square feet of sea floor. According to Mark Erdmann, their installation was one of the highlights of his career.

“These areas of the reef had been bombed in the 1970s, mostly by people from Sulawesi,” he’d told me. “But even after all this time, there was no recovery. The villagers didn’t understand why this was so; hadn’t they been forgiven?” The reason is that reefs are bombed where there are the most fish — and fish are attracted to a strong current. But that current also makes it hard for corals to grow back.”

The villagers asked for help rehabilitating the area, and Erdmann’s team crafted a Seacology proposal. Six hundred modules were brought over, and the local dive operators and community worked together to install them. A fleet of dive boats brought over the modules, and the villagers assembled them.

“It was fantastic,” Erdmann said. “Everyone, from little kids to grandparents, helped out. Then the dive operators came again, to do the underwater installation. But it was late December of 2003, and the weather got horrendous. Christiane and her people stayed until the bitter end — and we got them all in.”

On land, EcoReefs look attractive but artificial, like contemporary sculpture. Nearly two years later, they’re something else entirely: a hybrid of technology and organic life, like Jeff Goldblum at the end of The Fly. Their antler-shaped arms are covered with baby corals and sponges, more varieties than I can count. Parrotfish, Moorish idols and clownfish have set up shop beneath their limbs; two tiger cowries nestle near one’s center.

One of the techniques used to jump-start growth on the EcoReefs was “coral tranplants.” Chunks of loose coral were physically attached to the EcoReefs with little plastic ties. Oddly, those modules have done no better than the ones left to their own devices. No one knows why; perhaps corals, like delicate houseplants, favor a specific angle to the sun. When that orientation is lost, the polyps wallow in confusion.

Christiane busies herself with maintenance, using a dive knife to scrape a cauliflower-like soft coral that, unchecked, will cover the modules like an invasive weed. As she works, a handsome eagle ray — about six feet across — hovers nearby, watching with undisguised curiosity.

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In my early days as a diver I’d heard that damaged reefs would take a century to re-grow. It’s mind-boggling to see how fast these corals are returning. Moore has a lot of faith in his reefs — “If we build them, they will come” — but this growth would probably exceed his wildest dreams.

An hour later, back on the boat, Christiane lights a clove cigarette and shakes her head. “It’s incredible,” she says. “There are all kinds of fish; much more diversity than when I visited last. And at least two kinds of corals: acrophora, and millephora. Millephora, fire coral, is an especially good sign, because it means big boulders — coral heads — will grow. The whole area will become the foundation for a new reef. This is exactly what everybody was wishing for.”

We strip off our wetsuits, leave the boat, and wade in toward Nigiri. Pa (“Sir”) Ganche is the village chief, a big man with a broad face and fin-shaped feet. He meets us by his house, right next to the church.

“The population of Nigiri is 1,139,” he says. “The EcoReefs belong to everyone, and we all take care to see that no one is fishing in the no-take zone.” Free-diving, Ganche checks the modules at least twice a week. “The coral grows back much faster there than anywhere else; we didn’t expect it to be so quick!”

The terms of the Seacology agreement require them to wait five years before fishing here again, but Ganche and the villagers are unlikely to start so soon. “For the time being,” he says, “we don’t plan to fish there again at all.”

A second, smaller Seacology project lies in the waters near Alung Banoa, a village on Bunaken island itself. This effort has a sad origin; it was funded by Erdmann’s family and friends in memory of his brother Stephen, who died in a bus accident in Egypt in 2003.

But our attempt to dive at Alung Banoa site is thwarted by a powerful current. We make it as far as the underwater memorial plaque, in clear view of the 300 modules, when Christiane gives me an urgent signal to ascend. Divers caught in such currents can be swept out to sea, or down along the walls; victims of the Indonesian Throughflow they’ve come to enjoy.

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The next morning I meet with Pa Yunus, the local coordinator of Bunaken National Park, in Froggies’ open-air dining room. With his coiffed black hair and world-weary grin, Yunus looks like an Indonesian Clark Gable, around the time of The Misfits.

Yunus reviews the park’s figures with me. About 40,000 guests visited Bunaken in 2003, each paying a modest entrance fee (for me, about $18 US). This generated more than a billion rupiah — over $100,000 — in revenue. Eighty percent of this goes to park management, which includes boat patrols of protected areas, moorings, salaries, and a fund shared by the 31 villages within the park. The rest goes to Jakarta.

Yunus is mainly involved with the patrols — and they’re still needed. Last month, men were caught logging the hills on one of the park’s islands. But there was real drama in August, when a boatload of men were caught fishing illegally in the waters off Manado Tua.

“They threatened us with their speargun,” says Yunus, “but stood down when the park rangers showed their pistols.”

If convicted, the offenders may face 10 years in prison, or a 500 million rupiah ($50,000) fine. I ask Yunus if this is an excessive punishment, in a country where the average salary is about $1,000 a year.

“Everyone who lives here knows the law,” he declares. “When people commit a first offence we give them a warning, and try to teach them why preserving the reefs and forests is important. On a second offense, they are fined. But this was the third offense for these people. Of course they won’t have the money for the fine.” He adds, with a diabolical grin: “I think they will choose jail.”

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There’s a species of big-lipped wrasse on the Bunaken reefs, so colorful that one might mistake it for a parrotfish. During my final dive, I see one following me; it stays by my side me nearly 20 minutes, occasionally darting off to gnaw at the corals.

When I returned to Froggies and tell Christiane, she laughs with delight.

“Nine or ten years ago,” she says, “there was one wrasse — just one — who would follow people that way. The fish had figured out that, by doing so, it could leave its territory without being chased by other fish. Now, all the big-lipped wrasse are doing it. How they learned this from each other, no one knows.”

The encounter seemed a wonderful metaphor, and a hopeful note for the future. Someday, maybe all the creatures in Bunaken National Park will come to see humans as their allies — or at least as more sympathetic predators.