Catching my first glimpse of Palawan from the air, I began to understand why the province bills itself the “Last Ecological Frontier” of the Philippines. The long, narrow, jungle-clad island looks verdant and primeval, jutting from the Sulu Sea with a mountainous backbone cloaked in mist and sliced by intermittent waterfalls. Even from 23,000 feet, the main island and its orbiting islet spheres seem enormous. The archipelago stretches 280 miles from the Mindoro Strait south to the tip of Borneo, a constellation of emerald isles laced by tourmaline coral reefs.

Barely an hour’s flight from Manila, I touched down in hot, humid Puerto Princesa, Palawan’s only sizable town at about 250,000 residents. It is surprisingly prim, considering it’s literally carved from the relentless jungle. The main street bustles with scooters and townsfolk, small stores and markets, a handful of hotels and restaurants. It’s agreeable enough, but this countrified island capital is essentially a gateway to outlying excursions — the diving, boating, nature hiking and idyllic island lounging for which Palawan is known.

My first destination was offshore at Dos Palmas Island Resort, reached by a one-hour ferry transit into glassy Hondo Bay. En route I met resort staffer Ivan Lim, who explained what I’d already surmised. “In Palawan, we have a love affair with nature and are very strict about maintaining our ecological values,” he stated proudly. Case in point is the logging ban, passed in 1992 — not because plundering was no longer profitable, but because the island wanted to be taken seriously as an eco destination. The same eco ethos has taken root in town. Through its Operation Cleanliness, Puerto Princesa has won international awards as the cleanest, greenest city in the country. “Under the city’s anti-litter laws, a third offense carries a $1,000 fine plus two months in prison. That’s one reason we have such clean streets,” Lim added.

Such modern-day sensibilities are a far cry from Palawan’s untamed past. With a 1,200-mile coastline bounded by the South China Sea to the west and the Sulu Sea to the east, the island lies on the old Chinese and Spanish trade routes and was a refuge of pirates and the scene of World War II atrocities. It was famous for its old-growth hardwood forests of mahogany, narra and amagong, exotic woods prized for furniture-making and recklessly pillaged for decades. These spoils, including incredible fisheries and other natural bounties, drew generations of migrants from throughout Asia, making today’s Palawan a melting pot of 81 ethnic groups. Several indigenous tribes are still intact, like the Tau ’t Bato (“people of rock”) who live in the caves of remote southern Palawan. This no-man’s land has more in common with neighboring Borneo than the distant Philippines mainland and is so isolated, so rugged that an offshoot tribe of the Bato wasn’t“discovered” until 1997.

My stay at Dos Palmas Resort wasn’t nearly as rugged. The small, private island is one of 13 in the bay and perhaps the most opulent of all, with modern cottages and suites (some built over the water) decked with amenities and, thankfully, robust air conditioning. Being off the grid has spawned some island ingenuity. The resort has designated a chunk of the island as the Dos Palmas Eco Zone, where environmental programs, sustainable gardens and facilities that produce power and potable water keep guests content. And content I was, whether strolling through stately coconut palm groves, dipping in the pristine freshwater pool or imbibing at the elegant outdoor bar.

Being a bubble blower, I took advantage of the dive shop and explored shallow reefs a five-minute boat ride from the resort’s pier. Visibility was over 120 feet, so clear it was like swimming through air. Stingrays, seahorses, tuna, a kaleidoscopic collection of reef fish, along with all shapes and colors of coral, amounted to an underwater safari. My favorite site was Helen’s Gardens, named after a local woman who helped educate overzealous fishermen about preserving the beautiful reefs.

Just as the brochures proclaim, you get the sense you’re on the edge of a vast frontier in Palawan. At 6,575 square miles and with 1,780 islands, it’s the largest of the Philippines’ 80 provinces and has the highest concentration of islands while having the country’s lowest population density, roughly 641,000. Thumb through most any guidebook and the references to Palawan are the same: “thinly populated,” “hundreds of uninhabited islands” and “few roads with little to no services.”

I put this last claim to test when I embarked with a private driver on a marathon overland crossing to the famed Bacuit Archipelago and the El Nido Marine Reserve in Palawan’s northern reaches. But first things first. A couple of hours from town was Palawan’s signature attraction: a guided boat journey into the Puerto Princesa Subterranean River, a UNESCO World Heritage site.

The greatest part of this adventure isn’t cruising inside the subterranean spectacle but rather the 20-minute ocean transit from the village of Sabang on the roily South China Sea. Along with a few South Korean tourists, I hopped a wet seat on a banca boat — a huge dugout with spindly bamboo outriggers and an oversized lawn mower engine. Remember the wall of waves Tom Hanks crested during his island escape in Castaway? That was practically what we faced during our escape.

The limestone cavern mouth of the Subterranean River looks more like a placid lagoon than a cave-carving river. But once inside you see a rare spectacle that’s taken thousands of years to sculpt. Our little flotilla journeyed about three river miles as bats strafed our heads and our guide pointed out geologic features resembling natural gargoyles. At the furthest point we turned off our searchlights and experienced absolute darkness while dripping water rained over us and the screeches of bats echoed into the void. It’s a creepy place but remarkable in a Jules Verne-Journey to the Center of the Earth kind of way.

From Sabang I traveled the rest of the day and through the night to reach the village of El Nido. It’s a rollicking drive, negotiating potholes and deep puddles, ravines and small landslides. The thick rainforest is occasionally interrupted by towering white limestone cliffs sprouting like jagged sentinels above the jungle. Any clearings have become rice paddies with attendant kalabaw, water buffalo. As we passed through hamlets, I saw bronzed children playing au naturel while adults fussed with daily chores. When night fell, the cooling landscape became an inkwell in which the only illumination was the golden glow of cooking fires and lanterns emanating from thatched bamboo homes perched on poles. It was as if time had stood still here.

Bacuit Bay and the islands of El Nido are arguably the most stunning area in the Philippines. Limestone precipices crown most islands, which seduce you with their white-sand beaches and lazy coconut palms arching over the bluest of water. The sleepy seaside village of El Nido is the launching pad into the protected marine reserve, where I spent several luxuriant days diving, kayaking, beachcombing and fulfilling a near-castaway fantasy (with perks) at El Nido Resort on Miniloc Island.

Water is the central theme in El Nido, and I racked up a dozen phenomenal dives near surrounding islets. But you don’t have to be a diver to appreciate this water world. From the resort’s pier, guests snorkeled and tossed morsels of bread while the water erupted in a feeding frenzy of hundreds of colorful, and quite benign, tropical fish. Beach lounging, spa pampering, buffets beyond belief are all on the menu. But in my mind, the best offering was a half-day of sea kayaking on the island’s backside, where Big Lagoon and Small Lagoon awaited.

These are two of the most iconic, most photographed natural sites in all the Philippines — immense turquoise-colored lagoons surrounded by steep cliffs with flowering botanicals, alive with birds and monkeys. My guide and I paddled over the most gorgeous waters I’d ever seen, glowing with every imaginable hue of blue and green. Rainbow-colored fish darted beneath us while long-tailed macaque monkeys and hornbills shouted at us from above.

As we reveled in our surroundings, my guide talked about nature and ecology. “You can see why Palawan is called the ‘Last Ecological Frontier’ of the Philippines,” he said.

Yes, I nodded. “So I’ve heard.”

Info To Go

California-based Wilderness Travel offers 13-day guided snorkeling and kayaking adventures on Palawan starting at $4,495, not including international/domestic airfare. Philippines-based Lakbay Pilipinas offers a three-day Palawan package that includes the Subterranean River National Park and Puerto Princesa, costing $147 per person, and also books connecting flights from Manila. Visit www.palawan.ws.