​Change coming to Vietnam's floating market

Staying afloat is what all business people hope to do -- and it's particularly true for the ones Barry Petersen will be showing us in this Postcard From Vietnam:

It is barely dawn, and Do Minh Tu and her husband are already hard at work selling the pork broth soup she got up at 3 a.m. to cook. She adds in green beans, rice noodles, meat and Vietnamese spices pungent and peppery.

"You eat one bowl," she promises a customer, "you will feel full all day."

For 20 years she's been the best-selling soup lady at the Cai Rang floating market in the south of Vietnam.

"The buyers fight each other," she says, "to buy my soup."

This is capitalism at its best: big boat owners bring in watermelons and pumpkins, cabbages and turnips, garlic and sweet potatoes, from fields as far as 50 miles away.

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The Cai Rang floating market in southern Vietnam's Mekong Delta. CBS News

There is even advertising, of a sort -- sellers tie a sample of their goods, like pumpkins or garlic, to a pole.

At wholesale (as in, off the big boat), a watermelon might go for about 25 cents, bought by owners of smaller boats who will peddle their goods at a hundred-percent markup on the canals and streams of the Mekong Delta.

And there are other businesses amid the swarm of boats: a lottery ticket salesman, who can hardly keep up with demand. Or the coffee woman -- here, Starbucks comes to you!

One boat is like a floating 7-11 with sodas and snacks. Another is a bobbing sandwich shop.

And like smart business owners everywhere know, sales go better with a smile.

"Customers like to buy from sellers who are laughing and happy," Mrs. Tu told Petersen. "No one wants to buy from someone in a bad mood."