The partially submerged Hawaiian woman is nearly nude, her breasts barely contained by two seashells connected by a piece of string.

National Geographic, it seems, has found a new cultural frontier to explore: babes in bikinis.

"We wanted people to loosen up a little on the concept of what National Geographic is," says Editor Bill Allen.

Mission accomplished.

The century-old chronicler of far-flung societies is publishing its first swimsuit issue, a $9.95 glossy filled with women you might ordinarily see in a more sex-crazed magazine, like Sports Illustrated. But Allen portrays the project as being part of the publication's heritage.

"A lot of young men of a certain age grew up with National Geographic, and they were always waiting for the pictures of natives to come along," he says. At speaking engagements, he says, he's always asked: "Are you going to continue putting bare-breasted natives in the magazine?" (The answer is yes, and there are a couple in this issue, too.)

To be fair, the 120 pages are not completely occupied by scantily clad young things. There is a historical review dating to the 1900s, when women wore those full-length bloomers, and there are some pictures of flabby middle-aged women, children and even men (including a Belize native who seems to be in his underwear).

On the other hand, it doesn't exactly resemble the January issue, with a cover shot of a golden Egyptian death mask and such pieces as "Driving the Great Wall," "Japan's Winter Wildlife" and "Strangest Volcano on Earth?"

"People think of National Geographic, appropriately, as a very serious publication doing stories on the beginning of the universe and looking at countries like Sudan, where 2 million people died in a civil war," Allen says. "But the culture inside here is one that has a great sense of humor." The swimsuit extravaganza, he says, "could introduce a whole new audience to National Geographic magazine."

For a monthly that usually sells 9 million copies in 23 languages, the expected newsstand sales of the special issue, 250,000 to 300,000, are not that big a deal. But the media exposure -- there were so many inquiries that a planned embargo was dropped yesterday -- could be priceless.

First, though, the Geographic needed a hot cover. And the working cover -- a '40s Jane Russell type in a modest floral one-piece -- wasn't setting anyone's pulse racing.

So photographer Sarah Leen was dispatched to Hawaii, where she hooked up with a local shutterbug who shoots calendars and makes swimsuits -- including the one with the strategically placed shells. "I saw that suit and said, 'You've got to let me use that,' " Leen recalls. She put a shell-wearing college student in the water because "I wanted to incorporate the natural world so it made it more Geographic, and not just a girl in a swimsuit."

Not that there's anything wrong with that.

"I thought it was an amazing depiction of the world," Allen says. "You have rocks -- geology. You have water. You have those beautiful shells. And a very attractive young woman."

These folks have a knack for making the issue (also available at nationalgeographic.com) sound like a wholesome history project, with a news release boasting of the march of progress from "the daring bare midriffs of the 1940s to the tiny thongs of today."

The task of poring over the magazine's archives fell to picture editor Susan Welchman. This was harder than it sounds, for she had to go through hundreds of thousands of slides, none of which were categorized by attire, to find bathing suit photos. Then Allen made the final cut.

"I looked through several thousand pictures," he says. "I was absolutely astonished by what people will wear out in public." Still, he finds the shots modest compared with what he sees on television and in newspapers.

Allen became editor in 1995 and has wanted to do a swimsuit issue for about that long. So is he feeling like Hugh Hefner this week?

"There are wonderfully attractive women here, but it's certainly not a Playboy mansion," he says from the nonprofit society's downtown office.

Since women in swimsuits may be more marketable than, say, pictures of remote villages, could this become an annual tradition? Allen allows that he has enough leftover pictures for two or three more issues.

"I wouldn't put it out of the realm of possibility," he says.

History too: Geographic includes a worker sewing a bikini in 1969.The venerable magazine dove into its archives for its swimsuit issue.