An American heroine, a Nashville lass with a sweet, innocent Tennessee drawl and a shark's heart, is blossoming here -- right on schedule for a Moscow gold heist.

When Tracy Caulkins, 16, the freckled, blue-eyed sprite who is the hottest swimmer in the world, returns from the 1980 Olympics, she may need to head directly to Knoxville with all her loot.

These enervating Pureto Rican sauna days by contrast, are nearly a vacation for Caulkins, who, almost unknown to her countrymen, was America's top amateur athlete in 1978.

To be sure, she probably will win at least five gold medals in the first week of these Pan American Games -- more than anyone else in any sport, most likely. She started tonight by winning the 200-meter individual medley and sharing the gold of the medley relay team.

While ignorant world may gasp, that inner sanctum of folks here with watches, whistles and ear plugs -- those chlorine freaks who know that an "individual medley" is not performed by Linda Ronstadt -- are aware that Caulkins probably will waltz through specialties like the 400-meter freestyle, 100-meter breaststroke and the individual medley.

On a teen-age U.S. women's swimming team that is the most glittering squad in these hemisphere Olympics, Caulkins is the central diamond emerging from the rough.

This charming child has accomplishments that far outstrip her current fame -- there world records, five American marks and a Sullivan Award. But that situation will end during the next year.

Her picture is headed for every cereal box in America if her master plan works out. As she said today with startling seriousness, "I feel a responsibility to do something about those East Germans."

What Caulkins means is the East German swimming team, which humiliated the U.S. women's squad in the 1976 Olympic Games in Montreal.

These Pan Am games are just a stepping stone, and not a particularly momentous one, on her four-year path to Moscow.

For a high school sophomore who spends more than 1,700 hours a year in the water practicing, this week is a virtual respite in dry dock. To blaze through a qualifying trial in the morning, then come back at night to win her gold medal, is child's play for this mature person with braces on her teeth.

Whether she wins five or six golds here is presumed by most experts to be merely a matter of how many relay teams the U.S. coaches decide to use her on -- one or two.

What distinguishes Caulkins here, among thousands of Olympic hopefuls almost all her senior, is her ability to combine a sense of joy with a sense of mission.

"People ask me, 'Why do you do all that, practice all those hours?'" she said. "Well, it's something I've found that I do well. But most of the time it's just fun.

Under that easy Southern poise and disarming charm, which are most an indication of her self-confidence and natural grace than what she says, is an attractively dark streak of beat-'em-until-they-cry-uncle competitiveness.

When East German women, with their batteries of scientists, doctors and drug specialists, are mentioned, Caulkins' eyes narrow and she says, "I go to the doctor when I'm sick! if you have to win like that I don't want it."

When the U.S. women went to the '78 World Championships in West Berlin, the first off the blocks was Caulkins. She also was first out of the water -- with the first of her three gold medals -- all in world record time.

As the East Germans looked on, stunned, the American girls began cheering in German, "Guess who's back, U.S. women."

"Tracy seems to rise to the occasion. She understands that the whole U.S. team sometimes even the men's team, too, are looking to her for leadership," said Caulkins' father, Tom, a big, balding, bearded bear of a jovial man.

"Perhaps there's a little bit of heroine in Tracy," admitted her petite, intelligent mother, Martha. "I remember her coming out of the water in West Berlin and her teammates cheering, 'U.S. women, U.S. women,' at the East Germans."

"I don't know where she gets it," said her father. "All she got from me was crooked teeth . . . In the big meets, when it really counts, she has never lost. And that has eaten at a lot of people."

Certainly, one side of Caulkins' nature is that of the champion, which emerges as soon as she hits the water.

When she broke her leg two years ago, she insisted on continuing training, dragging a fiberglass cast behind her like an anchor as she kept up her six-hour-a-day, six-day-a-week, 11-month-a-year schedule.

Says her 18-year-old sister Amy, "If she had to rise from the water and run across it to beat you, I believe she would."

When Caulkins puts on her cap, straps on what she calls her "goofy goggles" and sticks out her jaw, she looks like some sort of implacable swimming machine. But out of the pool she is an average, happy teenager -- although an extremely poised and judicious one.

"I think that swimming has been a stabilizing influence on her life, rather than the other way around," said her mother. "She did not have high self-esteem as a young child. Swimming has helped her turn a corner, given her confidence."

Sometimes that confidence is astounding. At the swimming stadium today, after casually winning her first heat, Caulkins talked about the Olympic team she didn't make in 1976, when she did not get past the trials.

"I remember how disappointed I was and how bad I felt when the other girls did so poorly in Montreal."

How many 12-year-olds chastise themselves for missing the Olympic team?

"Tracy has a native competitiveness, but she's only competitive in swimming," said her mother. "She has it channeled.

"I admire her character. I often wonder, if I were in her position now, if I could put out like she is doing.

"Often, parents hold their children back in swimming. They can't bear to see their little girls in pain. Tom and I were both basketball players growing up in Iowa, and we were never afraid to hurt.

"To swim faster than you ever thought you could go, you have to go through a lot of barriers of pain. You hurt so much, but then the next day you find out you're still alive."

The Caulkinses are a warm and extroverted family, yet old-fashioned in some ways and big on dinner table debate.

"I sometimes wonder about the Depression and all the other hard times that American have come through," said Martha Caulkins. "I wonder if our kids could endure it.

"I think there are lean years ahead for our country -- all our problems and energy scarcities are coming to a head. I think our youngsters will do all right. But I worry. I see the German people, and even in one generation since the war they've gone downhill -- housing not as clean, streets not swept, floors not scrubbed.

"Our American children are given everything too young, then can't choose among all their freedoms. Tracy is lucky, in a way, that swimming gives her a focus through some difficult years.

"I remember how horrified all our friends were that we made our 19-year-old son buy his own car. They'd give their kids new cars, wonder why they wrecked them, get them repaired, then watch the kids wreck them again.

"They never figured it out. You only value what you earn, not what you are given. Tracy has learned that. Work brings results. Nothing else really does."

The Caulkins corollary to that theory is that children cannot be ordered, only prodded.

"Tracy is very susceptible to suggestions, if you plant them early enough," said her father. "When you're attempting a difficult thing you have to nuture the idea inside yourself until one day you say, 'well, maybe that's not too hard for me, after all.'"

The Caulkinses -- famous daughter and strong parents -- have an interesting mixture of knee-slapping laughter and serious far-sighted premeditation.

Tom Caulkins will call his daughter "green as a gourd," or a castigate a swimming writer who "doesn't know grunt from apple butter."

He loves to tell the story of his daughter's embarrassment not long ago when she wore "a particularly revealing swim suit" to try to save a few milliseconds for a world record.

"She might as well have beeen wearing nothing. She stood right on the blocks with those goggles and a big towel wrapped around her. She looked like she was going into the valley of death. Then when they raised the gun, she . . . woooop . . . threw off the towel, bent over real quick and dove in the pool."

Father and mother laugh.

"She has gone back to her old style of suit," said Tom Caulkins. "But a photographer caught her just as she threw off the towel. We've got it at home . . . for blackmail purposes."

As opposed to that spontaneity, the Caulkinses also are aware that they must plan out every detail of the next two years far in advance.

"It's tough," said Martha Caulkins, "to be known all over the world at 15, then retire at 17. That post-Olympic depression that many kids go through is no joke."

John Naber, winner of four gold medals at Montreal, has volunteered to help coach Tracy in the myriad pitfalls of the next 18 months -- both the winning of the gold and the capitalizing on it.

"Tracy is special," said Naber. "I don't think she's going to burn out like a lot of women in the past. She seems to get more pleasure out of practice than anyone else. I think she'll continue even after the Olympics.

"She's blessed with the ability to leave her intensity in the pool. When she walks around the deck, she's like any other 16-year-old. I've seen her at picnics and dances."

But Naber, a psychology major at USC, has grilled her in the past month as few 16-year-olds ever are, asking her every nagative, probing, busybody question which he knows all too well that a nosy world press will dream up.

Since swimmers tend to be anonymous -- their faces constantly in the water as they race -- Naber suggested that Caulkins acquire a catchy trademark, some recognizable trinket that might seem meaningless but would be worth millions of dollars when the day comes to market an Olympian.

Citing the Nashville connection, he suggested a coonskin cap as a goodluck charm.

As Caulkins emerged from the Piscina Escambron swimming stadium today, the first words she heard were Naber yelling, "Hey, Tracy, where's the coonskin cap?"

Caulkins screwed up her face in a teen-age "who-needs-an-old-coonskin-cap" expression.

"Well, if you don't want my advise," chided Naber, "don't ask for it."

The lanky Caulkins flashed her freckles and smile, shaking the water off her like a sleek young spaniel.

"Don't need it," she drawled.

As usual, how right she was. CAPTION: Picture, Tracy Caulkins Wears gold medal after winning 200 meter individual medley. UPI