ASSAM, India - The huge, one-horned beast looks up and gazes at us in the early-morning mist. Its thick, gray, leathery hide drapes down its flanks, like sections of armor plating. Two small birds perch on its rump, pecking away at insects. The rhinoceros is unperturbed by the birds or our close approach, allowing us to observe it at leisure from high above.

My wife, Annie, and I are riding atop an elephant through the grasslands of remote Kaziranga National Park in the northeastern state of Assam, India. Several other elephants, each with a mahout (handler) and two or three passengers perched on a saddle, cluster nearby. Cameras click away. Soon, we encounter a small group of water buffalo. They graze placidly, their broad, curving horns glistening with moisture. Later, we pass a herd of nimble swamp deer, dozens of them, racing away through the tall grass.

This elephant safari, and a separate outing by open jeep to another area of the sprawling park, are among the highlights of a fascinating cruise along the broad and powerful Brahmaputra River. On other excursions, we visit religious shrines, tea plantations, small tribal villages, and workshops where cotton and silk are woven into beautiful cloth. We become familiar with Assam, which is so different in many ways from the rest of India. Above all, we experience the vibrant and diverse daily life of people, flora, and fauna along this amazing waterway. Discharging more water than the Mississippi, the Brahmaputra is one of the world's mightiest rivers.

As we discover, it is also extremely tricky to navigate.

Arriving by air at Dibrugarh, we are met by a guide and driver and taken to board Charaidew, a small, but comfortable, shallow-draught ship that is to be our home for eight days. It features 12 simple, air-conditioned double cabins, all decorated with bright, hand-woven local fabrics. With a staff of 20, the personal service and dining are outstanding. The subtle Assamese cuisine uses somewhat milder spicing than most Indian food. Local fish, duck and other fowl, even river prawns, are freshly caught by the crew.

Our voyage takes us through one of the least-visited Indian states. "Just try to find a postcard to buy in Guwahati," the capital city of more than one million, says Udit, our guide. Connected to the rest of India by only a narrow neck of land, Assam is ethnically and historically more closely related to Burma (Myanmar), and so is its language. One traveling companion, Ayesha, is a sophisticated businesswoman from New Delhi. Raised in a diplomat's family, she has traveled the world. But she has never before been to Assam and does not understand a word when Udit talks to our driver in Assamese.

Our days on the river are a mesmerizing, otherworldly experience. Charaidew glides smoothly downstream with the current, between scoured low shores and barren sand islands, all of which will be obliterated by the annual flooding of the summer monsoons. Fine silt gives the water a milky look. The geography often resembles a moonscape, made all the stranger and more alien by the mists and morning fogs of the winter season.

And, yet, people eke out a subsistence living from the river's less-than-obvious bounty. They fish from small wooden boats of many sizes and styles and live in clusters of thatched huts that will be abandoned when the monsoons begin. At one of the sandbar islands, a couple of Muslim men come alongside in a tiny boat to chat with the crew. They tend hundreds of domesticated water buffalo, which are forced to swim out to the island to spend a few winter months, when there is grass for grazing. These nomads milk the buffalo daily and sell the milk to nearby villages.

Others earn money by harvesting swamp grass for thatch or animal fodder. Or by laboring under contract to the government river authority, building or repairing long structures of woven bamboo that are affixed to pilings in the shallows. Called "bundles," these concentrate the river's flow to create a somewhat deeper and navigable main channel. Like the seasonal fisherfolk, the workers live in crude, temporary encampments on the bleak sandbars.

Daily shore excursions give us exciting glimpses of life in the main valley of Assam, which is prosperous by Indian standards. There are oil and gas resources and extremely fertile agricultural land. Countless small home fish ponds line the roads. Udit's family's pond produced 55 pounds of fish in its first year, with increased harvests expected. Many think no day is complete without eating fish, and gifts of fish are traditional when families arrange marriages. We see very few beggars.

An economic mainstay is the cultivation of tea, Assam's most notable export. We enjoy lunch at a magnificent 500-acre tea estate owned by the same family for more than a century. Another local speciality is silk production and weaving.

The town of Sualkuchi alone has about 10,000 individual looms in cottage-industry workshops. In a courtyard, three women squat on the ground. One turns a crank while the others, with dexterous finger work, coax nearly microscopic filaments of naturally golden, and exceptionally rare, muga silk off a dozen silkworm cocoons that float in a pot of water. The resulting spool of thread is then passed along to highly skilled weavers, who work indoors at hand- and foot-operated looms. Gorgeous fabrics with intricate patterns result. Mahatma Gandhi once said Assamese women "weave dreams in muga silk." The prices for shawls and tailored garments are embarrassingly modest.

Majuli, perhaps the world's largest riverine island, is the epicenter of the satras, or monasteries, of Hinduism's distinctive Vaishnavite movement. It is dedicated to greater social equality and brotherhood among differing castes and tribes. We visit two satras that date to the 17th century, each housing several hundred monks. Young boys are taken in for a life of celibacy, prayer, and frugal hard work, largely on extensive agricultural holdings. Several monks invite us into their little apartments, or to have tea on the verandas outside. During one ceremony, the devotion and genuine enthusiasm are apparent as the monks, young and old, clap hands and burst into joyous chants.

At a temple dedicated to the god Shiva, I kneel to receive the blessings of a holy man, who puts the red spot on my forehead and ties a string around one wrist. We follow as devotees enter the dimly lighted inner sanctum with offerings of food, money, or sacred marigold blossoms. They chant a mantra as a priest blesses them with holy water splashed into their open hands.

A village of the minority Mishing tribe has simple thatched houses built high above the ground on stout posts to survive the monsoon floods. Underneath, the women have looms and weave vibrant cotton cloth. School is out, so a gaggle of friendly kids follows us everywhere. Piglets root around. Chickens strut and peck. Young boys wield slingshots to chase away thieving monkeys. Villagers invite us to climb wooden ladders and enter their homes, which are spartan. And, yet, there are signs of affluence, such as a few well-kept motorcycles. There is no electricity, but many have cellphones and little solar panels to keep them charged.

The winter river level is so low Charaidew runs aground repeatedly. A government navigation boat accompanies us, trying to lead us through the constantly shifting main channel. Suddenly, we hit bottom so hard a rudder is damaged. It will have to be removed and repaired at Guwahati in a boatyard. With apologies, our voyage must be cut short. In compensation, we are offered days at a wildlife lodge in Kaziranga park, where we first viewed the rhinos and water buffalo.

Owned by the same company as Charaidew, the Diphlu River Lodge has spacious bamboo-and-thatch cottages and fine alfresco dining. Our shaded veranda overlooks a narrow, meandering rural river. After the activity-packed cruise, it is tempting just to relax with a book and keep an eye out for storks and otters.

But there is so much to see and do that we opt each day for organized safaris or guided walks with Povi, the lodge's sharp-eyed naturalist. We ride an elephant at dawn once again, to get up close and personal with the park's 2,400 rhinos - two-thirds of the world's population of great one-horned rhinos. Bouncing along jungle tracks in an open jeep, we see eagles and ospreys and watch langur monkeys leap through vast banyan trees. There are tigers, too, but we see only a few tracks at water holes and claw marks on trees.

Hiking through a forest full of green parakeets to a rubber plantation, we see how the trees are tapped by the local Karbi tribe and the white sap is processed. Strolling through nearby rice paddies cultivated by Bangladeshi migrants, we watch them plow with pairs of young bulls and fish with nets in the river that flows past our cottage. Early in the morning, we hear the call to prayer from their mosque.

After each safari, the mahouts bathe and brush their elephants in the river. The great pachyderms spray themselves, roll over, and wallow in extravagant pleasure. It is a sight to behold.