What has 12 legs, spends much of the time under water and laughs a lot? Well, if you didn't say Montgomery County's Restrepo children, the first family of area swimming, get back in the pool and take another lap.

There are six of them -- Annie, Lisa, Patti, Diana, Maria and Louis, the youngest child and only boy. In fact, there's one for each lane of the Long Branch pool, where they have become the core of the swim team.

Very different in looks and demeanor, except for the capacity to laugh with each other, the swimming six would be seven, but Suzie graduated from the county swim league last year.

And although the Restrepo clan is believed to be the largest swimming family in the area, it certainly isn't the only one.

"We have a whole bunch of little kiddies," said Paul Vincent, president of the Montgomery County Swim League, which boasts 80 teams and more than 6,000 youngsters. "But only about half of them are Restrepos."

With competitive age groups from preschool through high school, teammates range from beginners to athletes such as former Montgomery Square swimmer Mike Barrowman, the world record holder in the breast stroke.

And with swim parties, team T-shirts, relay carnivals and the general all-around fun that go hand-in-hand with the swim leagues, the sport continues to grow in popularity around the Beltway.

The Prince-Mont League of Prince George's and Montgomery counties has 36 teams and more than 3,000 swimmers. The Northern Virginia Swim League, the area's largest, has 101 teams and more than 10,000 participants. Leagues also exist in Columbia and Howard County in Maryland and Prince William County and Reston in Virginia, to name a few.

With the large number of children participating, it's not uncommon for family members to become teammates.

For example, the Hillandale team includes five Solomons, while Eastgate features four Wises. Even the Restrepos have competition on their own team with four McKelpins. And the reason is simple.

"It's just really fun. It's a team sport as opposed to, say, tennis, which is individual. You have more opportunity for more kids to swim," said 18-year-old Maria Restrepo, who is also a member of the George Washington University tennis team. "It's something everybody can do. If I played tennis, I couldn't play with Louis or Annie, but I'll swim with them."

She'll also laugh with them, for despite the intrinsic competition, this is a family that gets along, well, swimmingly.

They've been known to tease 13-year-old Annie for organizing practice sessions in the backyard pool of their Ashton home. However, Annie has the last laugh, after convincing her siblings that she should race in the shorter lane of the pool because her long hair causes more drag.

Lisa, 15, is the focus of jokes because her musical tastes differ from those of her siblings. And Patti, 16, and Diana, 17, remain friendly despite competing in the pool and on the tennis court, where they are both ranked by the Mid-Atlantic Tennis Association.

Lisa helps Annie with her flip turns. The older girls counsel each other on strokes and strategy, and everybody gives 12-year-old Louis free advice.

"I hate it. They're always telling me what to do," he said with a grin. "Sometimes I try to do {what they say} and sometimes I don't."

But it isn't only the children that make Saturday morning swim meets such good, clean fun. The parents serve in many poolside capacities, including scorers, timers and judges, making summer swimmming a true family affair.

"It demands family involvement. It takes over 40 parents to run one swim meet," said Marcee Smith, president of the Prince-Mont League. "Sitting under a tree and sipping lemonade is out of the question" for most parents.

"We're a closer sport because we're right there on the field with the kids. We're right there on the deck," said Susan Kilmon, president of the Brandywine Parents Committee and mother of two swimmers.

At Long Branch, the Restrepos make a difference. They began taking swimming lessons years ago in anticipation of their backyard pool, and as their interest in the sport grew, so did their involvement.

They followed their winter swim coach, Herb Poe, to Long Branch in 1983, and two years later enjoyed their ultimate swimming moment when Annie, Lisa, Diana and Susie joined close friend Iona Brown to represent every age group and win the crescendo event at the league's annual relay carnival.

Currently, Louis and Lisa are among the top swimmers in their age group, and Lisa, Patti, Diana and Maria compete together on the girls 15-18 freestyle relay team.

Together they hold several team records, and it is not uncommon for the family to contribute as much as 35 percent of their team's points in a single meet.

"They are really good," said Long Branch coach Jayme Stroh. "They have their competition but for their division they are really doing well."

And Gustavo Restrepo, the clan's patriarch, sees more valuable lessons beneath the fun times and blue ribbons.

"The discipline is very important. The competition is important," he said. "In life, everybody is competing, so they learn how to win and lose."

Kilmon agreed: "As far as the swimming goes, it's a wonderful way to learn good sportsmanship. Their self-esteem increases because they are part of a team. The younger kids look up to the older kids, and the camaraderie and participation is just a nice thing to watch."