But it fucks you up, hope does. You internalize all that bad news about the planet, and then you see something like Raja Ampat, a place obviously still being born, and you don't know what to feel. Happy? Anxious? Exposed for a doom-and-gloomer, as the old armor of pessimism begins to crack and a whole new attitude raises its curious head? I felt stirred up from the very first dive—before the dive, really, when we were motoring to a site called Cape Kri, near Waigeo, and saw a Spanish mackerel leap out of the water, jaws inches from a desperate silver-shiny fusilier, predator and prey gracefully arcing ten feet into the air. Everybody in the skiff cheered. The sea was full to bursting with life, and we, like explorers in a time warp, were about to plunge into waters as wild as those of the ancient past.

About a thousand yards up-current from a classic mushroom-shaped islet, our Indonesian boatman cut the motor and we scrambled to sort out the gear heaped at our feet. Stop and drop: That's the drill for this sort of high-speed drift-diving. As soon as whoever's fins were on top of my fins got out of the way, I back-flopped into the blueberry-colored sea, kicking hard to catch up with my fleeing companions. We zoomed straight toward the island at a good three-knot clip, the water warm and uncannily clear. We could see the prow of the reef far ahead, where immense schools of barracuda and long-nosed emperor fish were balled up for feeding. Then we were among them, part of the collective chaos. The best critter finders among us searched out such masters of camouflage as the Papuan scorpion fish, its featherlike fins mimicking crinoids, and tiny oddities such as the orangutan crab, a fuzzy orange dead ringer for the great ape.

During the pre-dive briefing, Dr. Mark Erdmann, a marine biologist for Conservation International and a volunteer guide on this trip (his wife, Arnaz Mehta, is Seacology's Indonesian rep) with nearly 20 years' experience diving Indonesian waters, told us the currents that carve these Raja Ampat mushrooms are so strong that from the air the islands look like ships trailing wakes; in fact, one such island, mistaken for a Japanese ship, was bombed by U.S. pilots during WWII. We also learned that in 2001 Erdmann's friend and fellow marine biologist Gerry Allen set the then world record at Cape Kri for the most species of fish identified during a single dive: 283. So we were ready for the current and we were ready for the fish. But nothing can really prepare you for your first dive at Raja Ampat.

There are about 60 species of coral in the Caribbean; there are closer to 600 in Raja Ampat. And the reefs here support more than 1,000 species of fish, which means if you latch on to a good handhold and start counting, mental fatigue sets in long before you've stopped seeing something new. I hadn't realized just how low my diving expectations had sunk, kicking around hard-bitten, bleach-stricken, fished-out seascapes. It was as if I'd been diving for years on the undersea version of a prairie, and here at last was the rainforest.

After the dive, all of us aboard the Citra Bidadari had the same idea: Ransack the ship's library and put a name to some of the odder creatures we'd just seen. "I love it," business consultant Kris Billeter said. "Everybody's just totally nerding out with the fish-identification books." On the sofas of the saloon, we kibitzed and conferred, Macs on laps, UV cables downloading underwater shots to Paint Shop Pro. Bob and Rosie Heil had just come from China and Tibet; this was their second—or was it third?—trip to Raja Ampat. Suzanna Jamieson, from Düsseldorf, was nuts about nudibranchs. As my roommate, Eric Kanowsky, an IT-startup wizard, put it, "The more you dive, the smaller the things you look for." Everybody had done a ton of diving, and everybody rated Cape Kri among their best all-time.

During the morning's second dive, Sardine Reef, we drifted right into a school of bumphead parrotfish, four-foot monsters, about a dozen of them ripping at the coral like blue buffalo and totally oblivious to us. Sardine Reef is also a good place to see the green turtle—a parrothead with a shell—and the giant clam, a creature with no face at all but in a class of its own when it comes to color. Taken together, the two dives were like an entire career—and all before lunch. Kinda gets your hopes way up.

And this is the thing we shouldn't have believed but already half expected: Raja Ampat just kept topping itself. At dawn on the third day, the two Seacology boats, which had kept apart to avoid overcrowding the dive sites, steamed together into Mayalibit Bay, essentially unchanged since Wallace's three-month collecting expedition in 1860. At its southern entrance, the bay is as narrow as a river winding between mountains, an equatorial fjord, before opening up to an inland sea nearly dividing Waigeo into two halves. When Seacology had first approached Waifoi village in 2007 to see what they'd like to have in exchange for limiting fishing in the bay to traditional subsistence catches, they said they wanted sidewalks—nice, wide cement walkways to replace the dirt tracks that held puddles and mosquitoes and disease. And so, that noon, Seacology's board members and donors, festooned with crowns of trumpet vines, were given a hero's welcome, parading into the village center along that cement path at the head of a marching band of drums and fifes. Everybody was given a piece of cake and a seat in the shade. Babies cried, elders speechified, hands were shaken, and then all feasted on a spread of fish and swimming crabs and local mussels.

Ever the scientist, Sylvia Earle carefully examined an odd-shaped, snakeskin-textured fruit, took out her camera and photographed it from every angle, and then ate it for dessert. She was more effusive than anybody about the diving we'd enjoyed so far, though with a caveat. "This is the way it's supposed to be everywhere," she said. "A coral reef is a true metropolis, with millions of interconnected lives."