Quotes of the Day

The smoke of the village cooking fires mingles with the evening mist rising off the Kameng River as two Indian engineers appear on the balcony of the Dewana Hotel. Our heads are surrounded by a hungry halo of mosquitoes, and on the street below, a Nishi tribesman wielding a sword wanders drunkenly among yapping dogs — until a half-century ago, his people had engaged in the quaint practice of headhunting. "You're perfectly mad to come here for a holiday," one of the engineers bellows. "For us, this is a punishment posting."

The engineers' punishment posting is one of the reasons for my presence in Arunachal Pradesh, a northeastern Indian state. I had joined an expedition to raft down the Kameng, a savage, white-water river, which roars out of the high Himalayas through jungle canyons that are home to wild elephants, hundreds of orchids and three different species of leopards and tarantulas. The engineers' mission is to divert a tributary of the Kameng and harness its hydroelectricity, and this would be one of the last chances to raft the river before it loses its quicksilver fury. (See pictures of the turning points in Indian history)

The Kameng is also territory of the Nishi. Fierce forest dwellers, the Nishi wear a bird-beak hat (a fashion trend that has driven the Great Indian Hornbill to near extinction in Arunachal), carry a long sword and wear a stuffed rodent around the neck to ward off evil jungle spirits. I'm hoping to see real Nishis on home turf, not the sorry figure wobbling in the alley below.

Among my companions on this 12-day expedition are India's foremost expert on snakes and crocodiles, Romulus Whitaker, and his wife Janaki. They effuse about the hills along the Kameng being aslither with the incredibly venomous pit viper. Between the Nishis, the tarantulas, the leopards and the pit vipers, I begin to wonder if a trip down the Kameng is more than I'd bargained on. Luckily, our expedition is led by two of India's most skilled river guides, Yousuf Zaheer and Anvesh Singh Thapa, who supply cooks, tents and the oarsmen who will steer our inflatable rafts as we paddle like crazy through the 75-mile (120 km) stretch of whirlpools and roller-coaster rapids. (See pictures of Hinduism's sacred annual pilgrimage)

The Nishis gather as we prepare our vessels at the water's edge. "Is it elephant skin?" asks a boy, poking our raft. A Nishi unsheathes his sword from a monkey-fur scabbard, and waves it over his head, dancing. In broken Hindi, he calls out: "Hey! Next time, you bring me a foreign woman!" The Nishi has been impressed by the posters of Britney Spears and Christina Aguilera in a tea shop up on the road, and believes they may be worth a few wild cattle in trade. As we head into the current, a few younger Nishi gather on a bamboo suspension bridge above us, snapping photos on cell phones pulled from their monkey-fur pouches; in our wetsuits and helmets we are just as much an oddity to the Nishi as they are for us.

Within minutes, we hear the roar of rapids around a bend, and the jade-green Kameng turns into a washing machine tossing us around like dirty socks. Giant boulders rush toward us; the raft bucks and rears in the waves, spinning dangerously on the edge of a giant hole that appears in the water. "Left Forward! Hard!" shouts Eamon Maddocks, our guide, as a wave crashes over the bow, submerging us in a sparkling effervescence, an icy electricity. From far away, I discern Eamon's voice, yelling "Paddle! Paddle!" And I do, furiously.

For the next seven days, I never stop paddling as we descend nearly 70 stretches of rapids. There are moments of respite when the Kameng turns back into smooth jade, and we have time to ponder the misty jungle around us. An occasional hornbill glides by, its wings sounding like flapping canvas. Romulus finds plenty of leopard footprints in the sand around our camps, but no sign of the owners or the pit vipers. One night, we try to keep a sentry fire burning all night in the rain to scare off wild elephants. The fire gutters out, but luckily the elephants have better things to do than crush us like bugs as we sleep.

We find real Nishi, too. A shaman wanders into our camp, his hornbill cap adorned with a mirror and a majestic eagle feather. One night, three silent Nishi fishermen carrying torches pass our camp. We watch their silhouettes flicker and vanish into the steep night forest. They had lit torches to find their way, and to scare off tigers and evil spirits. I shiver, glad that we're on the river, and just passing through.

• Tim McGirk
• Well, O.K., the Nishi no longer seek human heads, but their fearsome reputation, combined with the vipers, tarantulas and leopards, makes a trip down the Kameng River reminiscent of Apocalypse Now