TAMARINDO BAY / RIO PACUARE, Costa Rica -- After dark, my brother Jay and I strolled back to our tent, anchored on the crest of a sand dune. The moon was high, and the tide was out. Swiping my foot across the sand, I carved bright comet streaks -- the magic of bioluminescence and moonlight. As we joked and reflected on the day, the sound of the surf on Playa Tamarindo soothed and relaxed us -- it was time to sleep.

Awake with the sun, Mike LaFace, Andy Castellano, my brother and I headed to Iguana Surf to rent surfboards for a day. We had spotted this undeniably cool surf shop and cafe the day before. A mosaic of Costa Rica's roads and towns was set into the floor. Racks of long boards were a welcome sight to the beginners in our group. We sat at the bamboo counter, ordered a round of smoothies concocted from fresh mango, pineapple and bananas and got the inside scoop on surf spots and primo places to eat.

We rented a few bruised boards and headed north toward Playa Grande -- Large Beach. Surrounded by dry, golden hills, this long, arching strand was how I imagined California's beaches were 150 years ago.

Today's waves were small and glassy. Mike, a Hawaii-trained surfer, was bummed. I, a rank beginner, was delighted. The sand was coral white and cool, and the water warm. As I spent the day paddling, falling, and occasionally riding, I began to understand the call of Endless Summer and the concept of a surfing safari.

As dusk approached, we headed to the Playa Grande Marine Turtle National Park, a renowned turtle-breeding zone. It was after dark when the guide's walkie-talkie finally crackled. A spotter called in news of a turtle making her way up the beach to lay her eggs.

Our guide turned on her flashlight with a dim, red beam to limit the light pollution, and led us along the shore. After 200 yards, we found the leatherback turtle just above the tide line. With slow, peaceful strokes, the turtle was digging a hole to nest her eggs. Once done, she turned and hauled herself back to the sea.

It felt good to be living in a time where humans would honor the trust of a turtle, and to be visiting a country that had managed to protect more of its land than any other in the world.

Take me to the river

The drive from San Jose, the nation's capital, to the launching point for the Pacuare (pah-KWAH-ray) River took a tad over three hours. By midday we were deep in a tropical forest, launching inflatable rafts into the swift, green river at San Martin.

It was March, the dry season, and the river was at its mildest -- a fun but not frightening Class III-IV (Class I is calm, Class VI is un-runnable). We had considered the cheaper option of running the 16-mile stretch in a day and returning to San Jose, but after glimpsing the unruly city, we decided to stretch the trip over two days, and spend the night in the outfitter's 1,000-acre eco-lodge.

Jay, Mike, Andy and I had commandeered the same raft. As we headed downstream, we saw no roads or bridges, only lush tropical forest. We heard no cars or planes, only the chatter of birds and the burble of water.

Our rafting guide told of us that monkeys, sloths and occasional deer inhabited the rain forest, along with more than 100 species of birds. He also explained, with evident sadness, that this section of the river and valley were slated to be dammed and flooded for hydroelectricity.

We coasted and splashed down the river as it cut its way through a sunny gorge surrounded by rain forest. The vines, trees, and brush were impenetrable -- so thick a child would have difficulty crawling through it. How did the Cabecar Indians, before the arrival of the machete, move about, or hunt to eat? How could they spot animals in such compressed vegetation, or stalk them quietly enough to snare them?

Around midafternoon, we paddled through the most turbulent set of rapids of the day and came upon Rios Tropicales' jungle lodge. A natural, "Swiss Family Robinson"-style structure, it seemed to grow out of the forest. To the right of the encampment, a stream and waterfall spilled into the Pacuare.

We tied off our rafts and entered the forest. The foliage poured out fresh oxygen, and the river and stream stirred a perpetual breeze. The soil smelled rich and alive. We clambered up a dirt trail to a split-log deck and dining area with an expansive view of the river.

We met the family who lived and worked at the eco-lodge year-round. A gaggle of children ran about barefoot, comfortable and free in the wilderness. We learned that their father had lost two wives and was on his third, Dina Obando, who lived in the jungle and ran the lodge. An outdoor, makeshift kitchen was tucked into the trees, and dirt trails wound their way from bunkhouse to bunkhouse.

As we relaxed on massive boulders along the river's edge, I spied Albert, the youngest boy of the family -- perhaps 5 -- wrap his arms around a bleached log nearly as big as himself. He lifted it, half-dragging, and scrambled across the river rocks and boulders that lined the shore. He struggled upstream for almost 200 yards until he was above a stretch of fervent rapids. He then dropped the log into the river, pushed it out into the current, and hopped on.

The log turned, rolled and finally stabilized as it sped into the rapids. Albert maneuvered himself until he was more-or-less on top. He bobbed on the surface, over, through and under waves, smiling and laughing all the while. When he reached a calm patch of water, he got out and went upstream for another run.

As darkness approached, dinner was prepared. Our guides and staff diced vegetables and meat by the light of their headlamps. When the dinner bell was rung, Dina diverted a small rivulet the size of a rain gutter by moving a stone. The diverted water ran down toward a car generator fitted with paddles. When the water hit the paddles, the car generator began to spin, powering 12-volt lights strung throughout the camp. Dinner was served.

It's a jungle out there

The sun makes its way through the jungle canopy slowly, and even more slowly at the bottom of a gorge, so rising with the sun wasn't early. After breakfast, we had half a day to explore the surrounding area. Jay and I headed to the neighboring waterfall and swimming hole for a morning dip. We proceeded inland, following the stream to a jungle-shrouded pool with a natural slide where we went to play in this natural Eden.

At 11 a.m., we met Johnny, our safety kayaker. He was the eldest son of Dina. A member of the Costa Rican Olympic kayaking team, he was raised in the jungle, and the intricacies of the forest came second nature to him.

We followed Johnny down a narrow trail. He explained that many of the trails in the forest had been carved by the Cabecar, the indigenous people of the region. We paralleled the river, climbing up and down hills and embankments.

I imagined trying to eke out a subsistence living from the forest -- I couldn't conceive of it: I would starve.

Johnny halted abruptly, drew his machete and held his hands out wide.

"Stop!" he yelled. We were in line behind him, staring at the trail. I saw nothing. I scanned the forest around us, and still could find nothing awry. What did our guide see that I could not?

"There, laying across the trail." He pointed. "It is brown, like a branch. Maybe 15 feet ahead." Still nothing. Then it moved. Slithered. Three shades of brown with black spots, like contoured bark on a tree, it was a snake almost 6 feet long.

"We should leave," said Johnny firmly. His machete still in hand, he turned, walked past us as he scanned the sides of the trail and led us back.

After a 10-minute silence, Mike asked, "Johnny, what kind of snake was that?"

"A fer-de-lance. They bite more people than any other poisonous snake in Latin America. One of the reasons we carry our machete is in case one bites us. We immediately cut off the limb that is bitten, or we will die. Most people die within one day if they do not. There is not other hope this far in the forest."

The rest of us were speechless. Had we taken this nature hike on our own, who knows what might have happened? Yet the Obando children play freely, floating the rapids, running barefoot in the jungle, helping cook and clean as part of a familial team. Papa Obando lost two wives to the forest. Had he lost children, too?

For the first time in my life, I really got the meaning of "It's a jungle out there." I understood the progression from airy natural huts to homes with doors, windows and bathrooms -- to keep the snakes and bears and spiders at bay.

As we mounted our rafts after lunch and headed into churning rapids with names like Lower Huacas, Cimarron, and finally Dos Montanas -- site of the proposed hydroelectric dam -- the wild and wooly rapids didn't seem half as frightening as a hidden tree branch that bites.

If You Go

COSTA RICA

Where to stay:

Tamarindo area:

Budget -- Cabinas Doly, $10 per person, 12 basic rooms, 011-506-653-0017.

Moderate -- El Jardin Del Eden: A five-minute walk from the beach, $60-$80 range, 20 rooms, 011-506-653-0137, www.jardindeleden.com.

Expensive -- Hotel Capitan Suizo: Right on the beach, eight thatched-roof bungalows ($160) and 22 rooms ($115), 011-506-653-0075, www.hotelcapitansuizo.com.

Pacuare River -- Rios Tropicales Lodge: River trip packages only, $250 for two days, all-inclusive, 011-506-233-6455, www.riostropicales.com.