Article originally appeared in February 2009 issue

The water at the entrance to Tham Morakot (Emerald Cave) is dark aquamarine. Dense schools of small fish make their way from alcove to alcove. In the air above, echoes clatter off the stalactites. The ocean reaches in like an arm and yanks out again. Under the water is silence; dark masses of fish drift in and out, and colors deepen. When the next wave flows in, a blowhole erupts, roaring in the resonant space. I turn on my diver’s light and see spume filling the air with a dense mist. I press on into the dark and, flipping onto my back, pick out jittering crowds of bats hanging from the ceiling; the acrid smell of their droppings fills the warm, moist air. Two hundred feet in, the cave brightens and I can make out creases in the wall through the clear water.

Soon I am flapping my way up a small beach into a place of light: a hong—a roofless room, a hole in the island. With sky above and cliffs soaring all around me, I stand in a huge, naturally formed cylinder, some 300 feet in diameter and a thousand feet high, the walls spectacular orange limestone formations green-dotted with tenacious trees. Birds flap in slow motion overhead in the blinding sunshine. My friends emerge into the light and walk forward, staring up and smiling.

The Emerald Cave is located on Ko Muk (Ko means “island”) in the Andaman Sea, off the coast of Thailand’s Trang Province. Our snug anchorage was a half-mile north, in a palm-lined bay, sheltered by the same towering limestone. Between the anchorage and the cave was some of the best snorkeling we’d experienced in weeks. Malaysia’s Strait of Malacca had offered up silt and pollution to an extreme we’d never seen on our circumnavigation.

When living on a boat, as John Scholberg and I have done on Ninth Charm, our 38-foot Dick Newick–designed trimaran, for ten years, clear water is a precious commodity that nourishes a healthy marine environment. Murky or not, the waters that flow from the fascinating island-city of Penang, in Malaysia, up the Andaman coast into Phang Nga Bay offer excellent sailing conditions, especially during the November-to-May northeast-monsoon season. The settled weather, precipitous karst islands, the fun-loving people and interesting cultural groups, and the excellent Malay, Chinese, Indian, or Thai food at a restaurant or two along the way make for truly memorable experiences. John and I cruised the area on and off for several months in the course of an extended circumnavigation, and locating clear-water patches became a bit of an obsession.

We discovered that between the line of latitude that runs across the top of Sumatra and the one that touches Phuket Island to the north is a 100-nautical-mile gap open to the Indian Ocean. Here the effluvial waters of Phang Nga Bay to the north and the silt from the Strait of Malacca to the south are flushed out, and the water is clear. We could once again share in the ocean’s three-dimensional world.

The island trio of Ko Muk, Ko Kradan, and Ko Ngai are part of the Lanta Marine National Park. The Butang Group to the south and anything westward within this 100-mile zone have the only clear waters in the area, until you cruise up the west coast of Phuket and north toward Myanmar. Also part of the park are the uninhabited island groups of Ko Rok and Ko Ha; Ko Rok offered the best snorkeling we’d seen since the Pacific, with several fish species and corals that were new to us in its extensive reef systems. It was here that park officers tried to make us pay twice the usual fee for a boat—and pay it per person, per day. But as soon as we took out our camera to photograph them, they took off in disgust. Disappointing, but it was only proof that cruising, like life—and the waters of the Andaman Sea—is never pure and simple.

Ko Muk also offered an excellent walk over-island through breezy small-hold rubber plantations. Once across the island, we turned south along the beach. As we neared the small town on the southeast side, the plastic and litter lining the path became thicker and thicker until we felt like Moses parting a path between two waves of packaging. Little effort is made to clear it away. What is cleared is burned in forest pits, as it is in most of the tropical world, or is left beneath the otherwise neat stilt-houses of the town.

These islands operate on a part-market-driven, part-tourism-driven, part-subsistence economy, and the border between the three is strewn with garbage. The combination of low awareness, a culture emerging from subsistence, and the ravenous demands of tourism has created an environment of unchecked consumer waste. Consider that at one time all objects used for containing food or carrying tools were made from natural materials. When they were no longer useful, they could be thrown aside to rot and regenerate the soil. But plastic packaging, cans, glass, and junk food have arrived in force even at these offshore locations in Thailand—and they don’t rot.

Toward the busiest parts of town, typical Thai wooden houses with swaths of bougainvillea and hibiscus lined the concrete pathways. In one open-sided structure, five women sat pounding curry pastes in large mortars. When I asked them if they sold their handiwork, they laughed and pointed me to the local shop. As always, the welcome of gracious Thai people and the kindness of strangers were truly heart-warming. My struggling Thai would produce exaggerated praise and questions about our rua-bai (sailboat) anchored on the other side of the island. We stopped at the small shops to buy vegetables and fruit and continued back out of town, through more plantations at the southern tip of the island to the Farang Beach (the tourist beach), where an arch over the road marks the start of backpacker’s lodges, restaurants, convenience stores, and a medium-sized resort. Here, the trash is cleared away, bushes are cropped, lawns are trimmed. From the beach, we hired a longtail open boat to scoot us around the karst to our anchorage. Longtails, ubiquitous in any Thai island tourist area, are powered by a diesel engine on a long pivot, with a 5- or 6-foot-long prop shaft with which the craft are skillfully maneuvered. In the evening, a shrimp fisherman knocked on our hull and we feasted on delicious Thai shrimp curry.

From the bay at Tham Morakot we would sail across to the south end of Ko Ngai or to the west side of Ko Kradan, both 40 minutes away. At the south beaches of Ko Ngai we picked up a national marine park mooring for a one-time 200-baht fee (about 7 dollars). Our boat sat over some spectacular snorkeling along an extensive fringing reef. We were delighted to find fish we’d not seen since the isolated Solomon Islands and corals we’d never seen before.

We observed classic examples of overdevelopment in Thailand, too. When the economy of a small area is utterly dependent on tourism, the families in the area give up their fishing and agrarian businesses, knowing they can make more money from the thousands of tourists that flood the Thai Andaman coast every year. In the more extreme cases on Phuket, Ko Lanta, and the Phi Phi Islands, you can find yourself besieged by everything from serious tour operators to unsavory shysters of every description. Wherever overdevelopment has occurred, we found murky water and damaged coral.

For example, in a small coral bay near the north end of Phi Phi Don, in the Ko Phi Phi island group, where we moored for the night, we counted over 50 tourist boats going by. While we were snorkeling in the bay, three longtails arrived with a tourist couple each. We watched as their anchors dropped on perfectly formed plate corals and anemones, breaking the coral and destroying the anemones. We railed at the drivers, but they shrugged. There is no regulation of these matters, and these shortsighted practices continue to destroy the beauty of these islands as well as future business. It was breathtaking and mind-boggling. At the famous Maya Bay on Ko Phi Phi Le, at four in the afternoon, we saw at least 200 boats—some with as many as 100 tourists aboard, all ready to snorkel or kayak around the bay. And this happens all day, every day of the year. Finding your way to the southern islands of Ko Lanta’s Marine National Park is worthwhile; it takes you away from the crowds.

The second time we went into Tham Morakot on Ko Muk, we were greeted on arrival in the hong by 200 Thai medical workers on holiday. They all hallooed a welcome and pulled us by the arm to place us in their holiday snapshots. The more sober participants discussed medical care in Thailand and their training, all in excellent English. We were taken into their warm community group, they laughed at us and with us, they talked to us about the plants in the karst and the formation of the hong. Then they loaded themselves back into their kayaks, turned on their headlamps, and sang their way through the darkness to their waiting tour boat. You’re never sure what you’ll get in Thailand: enlightenment during a personal journey; the beauty of an untouched natural spot; the changing consequences of tourist overdevelopment; or a great big group hug by delightfully open Thai people. Ours was a journey that often changed our expectations into reality, the darkness of a dream into a bright, sometimes painfully clear, reality.