CAI BE, Vietnam - The Bassac II chugs quietly down the wide, muddy Mekong River, swollen with recent rains. It looks just like the Mississippi - except with rice paddies and banana trees.

We are the tourist attraction.

"Hello!" children shout from the riverbank. Even the jaded fishermen watch the elegant teak and oak vessel as it glides past. On one bank is a brick factory with kilns in the shape of giant beehives. On the other, palm-leaf houses hide behind tangled vines.

Dinner is served on the Bassac's rear deck in courses - wine, delicate spring rolls, sea bass, fruit. The boat is built for 24 passengers, but there are just three of us - me and a honeymoon couple from Scotland, Jo and Jon who, fortunately for me, are in their trip's second week and up for air.

We linger on deck in the humid night, laughing and talking politics.

And suddenly it hits me. I am on the Mekong River in Vietnam. On a cruise. Eating banana crepes and drinking Chardonnay.

My, how the world does change.

American-Vietnamese relations normalized only 14 years ago, finally allowing tourism and trade between the former enemies. Now, Americans are third among nationalities that travel to Vietnam, with 333,000 visiting so far this year. Only residents of China and South Korea visit more.

Tourist cruises are popular on both the Mekong in the south and Halong Bay in the north. The Mekong is three hours west of downtown Ho Chi Minh City (better known as Saigon), while Halong Bay is three hours east of Hanoi.

Most cruises are one or two nights, but some are as long as six. Cost depends on what tour you choose and whether the trip is bought directly or negotiated by your tour operator, but generally it's about $250-$300 per night per person.

-Southern comfort: Mekong River

The Bassac II is just 2 years old and has 12 cabins. Constructed by hand of teak and oak, it is reminiscent of a typical Vietnamese fishing boat, but on a large, luxury scale.

Rooms have teak walls, private baths, soft beds and air conditioning and they smell of lemongrass. Passengers can lounge on the open front or covered rear deck; a bar is on the lower level.

The Bassac offers a few different itineraries, but mine began in the town of Cai Be and ended in Can Tho, famous for its "floating village" of fishermen and traders.

From Cai Be, the cruise takes a branch of the Mekong called Tien Giang, and then turns onto Cho Lach, one of the many canals that create a virtual highway of water throughout the Mekong Delta. In midafternoon, it stops near a village on the small Mang Thit River, which passengers can visit via a small speedboat (warning: it's hot and humid, so take water, sunscreen and bug spray).

There, you get a glimpse of ordinary life, where families live in palm-leaf houses surrounded by their dogs, chickens and children. Most have electricity and television. Before going back to the boat, you can have tea and a snack of pineapple with a local family.

After cruising a few more hours then anchoring for the night, the Bassac II starts at dawn, passes the floating market Tra On and then heads north to its final destination, the city of Can Tho.

For Americans, Can Tho's famous floating market is both fascinating and horrifying. You get to see the remarkably efficient trade between the farmers, fishermen and locals - a sort of Eastern Market on the water. You also see that everything organic - lettuce leaves, duck guts, human waste, pineapple stalks, soap suds - all get tossed into the wide, muddy fast-moving river. (Vietnam is just beginning to work on fixing its environmental issues.)

Me Kong means "Mother River." And that is what it is, the world's 11th longest river, winding 2,700 miles from Tibet to Vietnam, splitting into nine fingers of water through the delta to the ocean.

To be a dot floating on it just for one night was a pleasure.

And one week later, I would have another experience on a Vietnam overnight cruise - this one about 1,000 miles north at Halong Bay.

-Northern exposure: Halong Bay

Halong Bay is the top tourist attraction in Vietnam, with 3.8 million people visiting it so far this year. But the overnight cruise didn't start out too well. I could barely see the harbor because of the smog. Heck, I could barely spot our boat, the Halong Jasmine, anchored near the end of the dock.

The legendary emerald water was the color of khaki. The mysterious rock formations that make Halong Bay a UNESCO World Heritage site were swathed in a uniform haze.

"Mist" the staff called it. Sure, right, that's what China calls its pollution, too.

"It looks like LA," glumly observed a passenger from Orange County, Calif.

The sight of it made me sad. I had heard the bay was suffering from pollution caused by coal factories, and I knew that on many days, haze was a fact of life in the rapidly growing province of Quang Ninh, now with more than 1 million inhabitants.

So before I set foot on the boat, I realized I was about 25 years too late to see Halong Bay in any kind of pristine condition.

But within 24 hours, I still would be glad I came.

Halong Bay is on Vietnam's east coast, connected to the Gulf of Tonkin and the South China Sea. It is unique in the world because of its hundreds of huge limestone pillars sticking out of the water like God's knuckles or, as they say in Vietnam, dragon's babies.

UNESCO's World Heritage designation covers about 1,000 of the islands. To get out to them, you need to take a boat. I took the 10-month-old Jasmine, a 24-room boat owned by the Cruise Halong company.

With three decks, the Jasmine's decor was inspired by 1930s French Indochina, with satin curtains, teak beds and curved chairs.

Stable as a doctor's hand, even in choppy water, Jasmine headed for the UNESCO protected region.

For lunch, the 42 passengers were fed prawns, fish and strong Vietnamese coffee in a spacious dining room. Thus fortified, the Jasmine anchored for the afternoon off T Top Island, a conical-shaped tiny spit of land. A pretty crescent sandy beach welcomed swimmers. A 400-step climb to a vista enticed the ultra-hearty (but not me, are you kidding?).

We were hardly alone at the island. At least 27 other boats floated nearby. It turns out that Halong Bay has more than 400 tour boats, so many that this year the Vietnamese government has banned any new ones.

Ecologically speaking, I was indignant. Imagine, all those boats in a protected site! But then I noticed that the boats, with their colorful decorative sails, lent a picturesque quality to the scene. They were an addition, not detraction. They lent scale to the natural formations. Ah, a moral conflict! Instead of thinking about it further, I plopped into a deck chair and watched the scenery.

In late afternoon, the "mist" faded and the islands grew clearer. We anchored near a fishing village with about 80 brightly colored floating houses. Steep vertical limestone cliffs loomed above. Dogs barked. Voices floated over the water. Some of Jasmine's passengers went kayaking. Astonishingly young children - ages 4-7, it looked like - paddled out alone in tiny bamboo and wood boats to sell shells and drinks.

As the sun went down, a crescent moon rose. Tiny lights went on in the houses, powered by electric generators. A thumping Vietnamese version of hip-hop blared through the dark.

Quang Ninh province's department of tourism predicts 4.8 million tourists to Halong Bay next year. So it is easy to worry. Vietnam seems to be risking its most fabulous tourist attraction in the name of progress. Although it has put new restrictions on boats, air pollution must be stopped. Why? The most beautiful boats in the world, the best food, the best service don't matter if your natural wonder is enveloped in smog.

Still, like the Bassac, the Halong Jasmine was a pleasure to board. Well-run, efficient, excellent service, good food and rooms that looked more like a hotel room than any cruise ship made the visit, despite my misgivings, guiltily enjoyable.

---

IF YOU GO:

GETTING THERE: Fly to Tokyo, Seoul or Hong Kong, then to Hanoi or Ho Chi Minh City (Saigon). Vietnam Airlines is reputable for flights within Vietnam.

CRUISES: Most tourists take overnight cruises as part of a larger tour. If you want to book directly, contact Cruise Halong (Halong Jasmine) at www.cruisehalong.com. Contact Trans Mekong (Bassac II) at www.transmekong.com.

Prices vary, but in general, it costs about $270-$300 per person per night for these and similar cruises.

TOURS: Most first-time visitors take a tour. I used Ann Arbor, Mich.-based Journeys International to book my tour, which included the two cruises and a land-based tour that included guides and drivers, for about $3,900, not including airfare (www.journeysinternational.com, 800-255-8735).

Reputable Vietnam-based tour companies that can book cruises include Trails of Indochina (www.trailsofindochina.com) and Buffalo Tours.(www.buffalotours.com).

OTHER DETAILS: Visa: You need one for Vietnam; it costs $65. Get it through a visa expeditor such as American Passport Express (www.passportexpress.com).

TIME: Vietnam is 12 hours ahead of Eastern Standard Time.

MONEY: 16,000 dong equals $1. However, you can use U.S. dollars to pay for virtually anything.

ELECTRICITY: Vietnam uses 220 volts (vs 110 in the U.S.) but outlets use the same plugs as here. Camera, computer and cell phone chargers work.

VACCINATIONS: Consult a travel medicine clinic or www.cdc.gov for immunizations needed - Hepatitis A and B, typhoid, plus polio and tetanus boosters. Malaria risk is low except for rural areas.

LANGUAGE: Many Vietnamese in tourist areas know some English, but you likely will need a translator in out-of-the-way spots.

---