Michelle Griglione, this country's best all-around women's swimmer, was awash in practice in a humid, dark building at American University, churning though the water to the beat of her own rhythmic kicking. Every couple of strokes, she slid her head up just high enough to drag some chlorinated air into her lungs and continue on.

Back and forth she went, crossing the wakes and riding the waves produced by the dozen other high school kids with whom she shared the pool's four lanes. Except for short breaks to catch her breath, this went on for two hours.

Her coach, John Flanagan, sat on a wooden bench and watched her go.

"There are bigger girls," he said. "There are stronger girls. There are girls with more God-given stroke talent. But they aren't like her. There is no one like Michelle."

In March, Griglione, a senior at T.C. Williams High School who is not yet 17, won six national titles at the U.S. Short Course National Swimming Championships in Orlando, Fla. Three were individual races, including both individual medleys. Three more were relays she swam for the Curl Swim Club, which won the women's national competition. No other swimmer there won as many races as she did.

Griglione (pronounced Grig-lee-OWN) specializes in the individual medley, swimming's mini-decathlon, the event Tracy Caulkins bequeathed to the younger generation when she retired after the 1984 Olympics. It's natural for outsiders to take one look at Griglione's recent results and jump to the conclusion that she has filled the void Caulkins left.

In this case, it's not only natural, it's also right. She is 3.3 seconds behind Caulkins' U.S.-record time in the 200-meter individual medley; 6.5 seconds behind her in the 400 individual medley. It's not unreasonable to expect her to drop a couple of seconds this summer. She has defeated the Soviet Union's rising star, Elena Dendeberova. By the 1988 Olympics, who knows?

"She's the best women's swimmer we've got right now," said Charlie Hodgson, an assistant U.S. Olympic coach from Miami. "There are swimmers who are better in their specialties, but if you need one swimmer overall, right now, you'd take her."

Yet life is never as uncomplicated as it appears within the lane ropes, where you follow the black line on the bottom to the wall, only to turn around and come back through the same water again and again.

Griglione's story only begins in the pool. She is a straight-A student in honors courses. She is going to Stanford University to be an engineer and a swimmer, in that order. She speaks fluent German and occasionally performs some off-the-cuff interpreting at international meets. She plays one mean piano.

More? She is completely undistracted by teen-age things. She watches only one TV show a week, Bill Cosby's. An only child, she says she is a homebody. She politely avoids most interviews because she would rather her teammates get the attention.

"I don't swim for the publicity," she said recently at her family's modest brick home in a working-class neighborhood of Alexandria. "Swimming is something I absolutely love to do, and that is why I do it. I've never done anything else. This is all I've ever wanted to do."

When you think of swimmers, you think of waxy blond hair and deep tans and leafy country clubs. Griglione has none of the above. Her parents, who married and had their daughter as college students, laugh that she perhaps never would have gotten into swimming if the local pool in Ames, Iowa, hadn't been free.

Rick Curl is the namesake and head coach of a nomadic swim club that has no one pool big enough for its needs, yet still beats many of the splashy California and Florida teams. When he replays all the races he has watched Griglione swim over the years, one split she didn't win comes to mind. It happened at the nationals in Orlando, in the 400-yard medley relay. Griglione was asked to swim the breaststroke, which probably is her weakest stroke.

"We didn't have anyone else to do it," she said.

The Curl team had a small lead when she dove in. But the second-place team, from California-Berkeley, just happened to include Hiroko Nagasaki, the Olympic gold medalist in the 200-meter breaststroke. In a 100-yard race, it seemed a lock that Nagasaki would win easily.

Nagasaki did indeed catch Griglione in the first 50 yards. But she never did pass her. They swam side-by-side until they touched.

"I was not going to let her get by," Griglione said.

The last two Curl swimmers in the relay beat the last two Cal swimmers, and the race was won.

"Without Michelle's split in that relay, we don't win," Curl said. "She performs better in meets than any other swimmer I've ever seen. She performs at a high level even at the low meets. I'd equate it to a player going all-out in a preseason game. It just rarely happens."

Swimming coaches love level-headed swimmers, but because swimmers peak from their mid-teens to their early 20s, swimming coaches almost never get what they want. Often, these coaches spend more of their time drying tears than they do pushing stopwatches.

Yet everyone who has been associated with Griglione, from the time she became serious about swimming at age 7 until now, says she has never been a problem. No one could remember a fit of rage, or even a mini-tantrum. If she gets mad, she keeps it inside.

"I wonder if anyone is as consistent as she is," Flanagan said. "That makes her a very dangerous competitor. It means she will not beat herself."

At the nationals, Griglione was the only woman who did not "shave down" for the meet, Flanagan said. When a swimmer shaves his or her body, it is a statement: "I'm ready." In many ways, it's more mental than physical.

Yet Griglione didn't do it. Flanagan said she looked over the field, considered her upcoming summer schedule, which likely includes the world championships in Madrid in August, and shrugged her shoulders.

"She said her best would just have to do at that moment," Flanagan said. "It's amazing she would have the confidence to say that."

Her life seems to spin on the axis of swimming. She awakens at 4:15 a.m., that spot on the clock reserved for morning talk show hosts and avid swimmers. Her mother drives her to American for 4:45 team practice. She comes back home, eats breakfast and gets to school at 8:30. When school's out at 2 p.m., she goes home, does her schoolwork, swims from 4 to 6 p.m. at Lee District Pool, eats dinner, plays the piano and goes to bed at about 9.

But if you think swimming is everything, consider this: She turned down swimming trips to Brazil and Europe so she wouldn't miss school.

"There will be other trips," she said. "I hope."

Even though Griglione spends so much of her time with her parents, she is neither sheltered nor naive. At the recent U.S. Open meet in Austin, Tex., Griglione, who learned her German in high school classrooms, was waiting with the other swimmers for their race to begin when an East German girl received some advice from her coach.

Griglione eavesdropped, then smiled and immediately told the U.S. coaches and swimmers what the East German had said.

"She's going to false start on purpose," Griglione said.

The East Germans were hoping for a psychological edge by disrupting the race, but the Americans knew what she was going to do and followed her right into the water.

Several other times, U.S. swimming information director Jeff Dimond has asked Griglione to help when he needs to talk to the East Germans and the interpreter can't be found.

That may stop. One of the U.S. coaches recently asked Dimond to look for the interpreter before looking for Griglione.

"They said, 'Remember, she's a swimmer first,' " Dimond said, laughing.

Griglione, 5 feet 10 and 130 pounds, comes from an athletic, driven environment. Her 6-foot-2 father, John, a former defensive tackle at Iowa State who tackled Kansas running back John Riggins a time or two, now rides his bike to his administrative job at the FBI. He came to town from Iowa with a map in his pocket, leaving his young wife and daughter behind in married student housing.

He found an apartment in Alexandria, then called for them to come.

"We were so pleased," said Carolyn Griglione, who is 5 feet 11 and a former Iowa girls basketball player. "All we wanted were the three B's: a basement, a back door and a bathtub. In married student housing, we all talked about the three B's. We didn't have any of those."

Carolyn Griglione taught preschool, but her No. 1 passion was her daughter. She scanned the newspaper, always looking for different things for the two of them to do.

One day, they watched an elephant help erect a circus tent. "It was something fun to do," said Carolyn Griglione. "And it was free."

They rode the Metro the first day it opened. "It was the Red Line," said Carolyn Griglione, adding with a smile, "and again, it was free."

In 1974, when Michelle was five, they read about a swim meet in which Melissa Belote, winner of three gold medals in the 1972 Munich Olympics, was going to race. They went. "You guessed it. It was free," said Carolyn.

The rest, as they say, is history. Michelle Griglione, who had been paddling around in pools up until that point, started to get serious about the sport. Soon there were practices and car pools and ribbons accumulating in the bedroom.

When she was 10, she came home from a meet, and, from her room, yelled her time in the 100-yard individual medley to her father in the living room. He leafed through a book of national age-group records and came upon the 10-year-old girls' record. He was shocked to find that his daughter had broken it.

"What?" Michelle yelled.

The Grigliones immediately called her coach at the time, Lou Sharp, to ask him what they should do. They were able to reach the official scorer at home, get the sheet on the race and send it in to get her time certified.

"We just knew there was some piece of paper somewhere with the time on it," John Griglione said.

Five years later, she was swimming in the U.S. Olympic trials in Indianapolis. She entered seven events, more than any other swimmer. "What else did I have to do?" she asked.

She missed the Olympic team by 9/10ths of a second in the 200 individual medley and by six seconds in the 400 individual medley, both won by Caulkins at the trials and the Olympics. If she had made the team, she would have been the youngest U.S. Olympian, and almost certainly would have been a medalist.

She doesn't lose much anymore, and although she looks ahead to 1988 only in her dreams, she eventually might be favored to win a gold medal. Or two.

"You know, I've never been able to completely figure her out," said Curl. "I'm not sure exactly what drives her, why she is so good. All I know is, it's all there. She's completely together.

"If only they all could be that way."