I Tan, Therefore I Am : Think of them as the magnificant seven of Marina High. These girls of summer are full of fun and low on worries, and the nearly endless season is one long day at the beach.

Admit it. The reason we wax nostalgic over youth has nothing to do with unpredictable body changes and everything to do with freedom.

Despite curfews and rules, not being able to legally drive and occasional bouts of freaking out, those teen years when we start high school and just before we get our driver’s license can prove the freest in our lives.

Free to eat anything without counting calories. Free during vacation and weekends to stay up all night chatting with your very best friends without worrying about waking up early for work. Free to relax in bed all morning and do whatever the rest of the day.

And in the summer, when freedom rules, “whatever” usually means a daily bake at the beach if you grew up within 15 miles of the coast.

Like some biological clock that kicks in the day after school ends, the cycle goes like this: wake up 9ish, rise within the hour and make phone calls, watch a soap (yes, dudes watch soaps), then get on the bus or your Schwinn Cruiser and head to the beach.

It’s an almost daily ritual for gangs of good friends like the seven Marina High freshman I met up with who have become a fixture on the sands of Surf City, U.S.A.

It’s a tribute to their conversation skills that they can spend nearly every breathing moment together. Most nights they sleep over at one of the girl’s homes, after an evening of the movies, parties or just hanging out. Those who don’t have to spend their mornings at summer classes sleep in.

Once in a while Amy Conti, 13, videotapes “All My Children” if it’s going to interfere with getting to the beach. She and her six girlfriends rely on the bus or a parent to get them to the pier at Main Street, although arriving at the preferred 1 o’clock doesn’t always fit into Mom’s plans.

It’s at this city beach, between the pier and lifeguard Tower 2, where they spend about 20 to 25 hours a week.

“This side is where all the surfers are,” says Natalie Hallett, 14. “Lots of families go on the other side (of the pier).” So do bodyboarders, who don’t rank as high as their surfboarding counterparts in Natalie’s and her pals’ book.

“There are more cuter surfers than bodyboarders,” continues Natalie. “I don’t why. They’re just older. They’re cuter.” Nearby, Jessica Cashman, 13, and Kelsi Black, 14, nod in knowing agreement.

Such information counts during these warm, endless days. As much as they enjoy the Pacific’s natural attributes, the fact that guys add to the landscape makes the scene all the more paradise.

But it’s mostly a looky-loo experience. After seeing the same guys for a few weeks, they might finally introduce themselves. Even then, the “relationship” stays at the beach. It’s not about finding a boyfriend, they say. Just uttering a quick “hi” and occasionally striking up conversation.

As for the dudes who check them out, Amy says it’s fun. “Except when it’s some sick, old, 40-year-old guy. Gross!”

*

From where they lounge, an indiscriminate patchwork of oversized towels covers parts of the sandy ground, each with its own stock of plastic bottles.

There’s spritzer water to refresh the skin and mineral water to drink, bronzing oil, hair lightener, moisturizer. Ragged issues of Mademoiselle and Seventeen get passed around. Piles of jeans (cut off or long and extra baggy) and T-shirts lie crumpled next to backpacks of every design imaginable.

These seven bikini-clad maidens, like hundreds of their peers along the coast, live out the days lying out, swimming, people-watching.

So do they watch who’s hot and not? They remind me that they’re not there to look at girls. Still, a perfect body can’t go unnoticed, no matter how many times the admission is accompanied by by “I don’t really care.”

“I don’t,” Amy says. “I maybe wish I was like them. But I don’t really care. Well, I mean I do a little.”

Saraeh Gregory, 14, says it’s not an issue of competing with the beauty queens, most of whom, she adds, are older. Besides, she says, “there’s lots of guys here.”

*

When they grow tired of their towels, the girls cruise. They walk up and down the pier, where they can get a better view of it all (“It’s a good place to check out guys,” confides Amy).

Main Street Promenade proves better than any air-conditioned mall. You can walk in and out of the shops in a swimsuit and shorts, and no one sneers. You can shop at cool stores that stock beach, alternative and secondhand gear. And there are coffeehouses, Burger King and plenty of other tasty stops.

About $20 a week goes to the local eateries, each girl figures, for burgers, fries, burritos, sodas and other oozing, fried and carbonated grub. Most kids at the beach might look like the quintessential picture of health, what with their lean, toned and tanned figures, their fresh faces and cottage-cheese-free thighs. But a closer look, say to the greasy wrappers next to them, prompts some questions.

Back to the freedom thing. The average teen can consume anything and it won’t show. Amy and company keep reading magazine articles about eating right and exercising. They figure they’ll heed the advice and warnings eventually, maybe even tomorrow. A couple of them try to as part of their sports training. But ask who wants a dripping cheeseburger from Johnny Rockets, and all admit it’s tough to say no.

“I guess we’ll care about it later,” Amy says.

*

Pushing it off until manana is an integral part of the youth game of life, especially when it comes to factors such as junk food, lack of sleep and SPF. What about SPF? The subject of the harmful effects of overexposure to the sun halts the conversation among them. They look at each other and start laughing, somewhat nervously.

“Yeah, Ill probably worry about it later in life, like my mom does,” Amy says.

Jackie Candipan, 14, agrees. “I don’t really think about using sunscreen, because I want to get a tan. I’ll probably be more conscious about it later. My older sister scares me sometimes talking about the dangers. She loads on the sunscreen. I do sometimes, but I’d rather use tanning lotion.”

“Hey, we’re just kids,” adds Sarah Shuck, 13. “We have the rest of our lives to worry about that stuff. We only do it for two months, and then we go back to school,” she adds.

Let the burgers and Cokes flow. Let the sun blaze. After all, a reality chock-full of bills, deadlines and responsibilities is just a few summers away.