NEW YORK — For most women, shopping for a bathing suit is not on top of the list of favorite tasks. There are unflattering lights to deal with and sizing that seems to make no sense, bringing up all sorts of body image issues.

The least swimsuit manufacturers can do is offer a full range of shapes and styles upping the odds that eventually shoppers will find the best one, right?

Shoshanna Lonstein Gruss thought so. But as a tween and then a teen, Gruss struggled finding a suit that would fit her frame that was petite everywhere but her bust. It was a source of frustration and embarrassment. When she chose a career in fashion design, she made rethinking bathing suits a priority.

"It didn't make sense that swimsuits were in sets. You wouldn't buy your lingerie in sets," she says.

On a recent browsing expedition through the swimwear department at the flagship Bloomingdale's on the Upper East Side of Manhattan, Gruss points out that many companies now offer bathing-suit separates and tops based on bust size, as her line does, instead of dress size.

She's not claiming to be the first designer to do these things but she does think the rapid growth of her swimwear collection since it was introduced in 2001 certainly helped nudge the industry forward. She began with only a handful of bikini styles and has seen it grow to include 40 prints each season, tankinis and one-piece suits, which she added after she became a mother in 2005.

Gruss thinks she owes that success for not only understanding her customers but because she is her customer.

"I remember being here with my mom. I looked 29 when I'd put on a bathing suit because the styles that fit me were either too old, too sexy or nothing fit. That was the worst feeling in the world when you're 13," she recalls.

Because she was athletic and wanted to be able to move around without worrying about falling out of her bathing suit, she often resorted to a big baggy sweatshirt as a cover-up that rarely came off. Again, not really a look coveted by teens.

CAREER PATH

Gruss went on to the University of California, Los Angeles — bathing-suit country — and earned degrees in history and art history. After that she went to work at a lingerie factory to learn about fabric, construction and design. Her personal experience as a hard-to-fit figure has influenced everything she's done since launching the Shoshanna label in 1998.

She first produced sundresses because they were easier to market. In 2001, when she introduced swimwear, it was a personally important moment. Then, following the birth of her daughter with husband Josh Gruss, she added children's swimwear under the label of Shoshanna BabyGirl.

Now that she's 31, Gruss is looking for something different from her bathing suits than she did in her single days. She's still trim and petite — and she's still busty — but now she needs to be able to carry around her daughter, build sandcastles and even dive in the water on little Sienna's command. However, she doesn't want to sacrifice style.

Gruss is, after all, part of the socialite set that is photographed regularly, including when she's at play in the Hamptons. For a recent — and childless — trip to Jamaica for a wedding, Gruss packed five suits: a pink gingham triangle bikini, two bandeau bikinis, a black eyelet bikini with a halter top and a white eyelet one with a strapless bra top.

"This is to look cool in front of my friends. If my daughter was coming, I'd have a one-piece."

LOTS OF OPTIONS

The Bloomingdale's tour starts in her own section. Gruss emphasized that her tops, both for one-piece and two-piece suits, are offered with cup sizes from A to DDD and in either petite/small or medium/large back widths, similar to bras. (The line is primarily intended for women who wear a dress size of 0 to 12.)

By using an underwire bra construction with 26 components, including boning on the sides, silicone gripper tape at the top and a classic hook-and-eye closure in the back, Gruss is confident her strapless tops will stay up on women of all bust sizes. They won't flatten a large chest or slip on a small one, she says.

When you're in the dressing room, stand up, sit down and move your arms to make sure the suit fits, she suggests. "If you think you might fall out in the dressing room, it's definitely not a suit for racing or swimming laps."

Gruss thinks a teenager might gravitate toward a halter top, perhaps in eyelet or a Madras print, because that silhouette offers the most coverage if she chooses to play a beach volleyball or actually swim.

Conversely, though, the coverage from a halter might also appeal to an older woman who isn't interested as baring as much as she used to.

That doesn't mean this woman isn't sexy, Gruss says. She says a halter-style one-piece, especially one with ruching and boning — both tools to support and flatter one's figure — conjures up images of Marilyn Monroe.

A triangle top, especially as part of a string bikini, defines your shape, Gruss says, so it works well on a woman who feels her breasts are of unequal size. Also, she adds, since it's often adjustable at the neck, it's appealing for someone looking a little lift.

In general, suits with higher backs have more support, and crisscross straps are sturdier than tank straps.

Gruss points out a green one-piece by La Blanca with a shirred bodice, which hides a multitude of flaws, and then a Michael Kors one-piece with a plunging V front that's laced together with a chain.

The Kors suit creates the "illusion of perfection," she says, because who else would dare wear such a suit than a perfect woman?

Except that, upon close examination, it's not that racy. Gruss highlights the high back, built-in cups and full-coverage bottom.

The tankini is a phenomenon that Gruss doesn't quite get. She sees the appeal of a sportier style but it often comes off as a little matronly, she says. If you're going to wear one, make sure the top meets or covers the bottom and try a youthful, trend-right baby-doll style.

Gruss identifies other key looks for the summer of 2007: geometric or nautical prints that have a 1970s jet-set vibe; the sweet sexiness of a full-coverage, Brigitte Bardot-style bikini in a gingham or eyelet fabric; or metallics. Gold, she says, is flattering on almost any skin tone.

"Swim is always all over the place but this year is very feminine, very celebratory of the body," Gruss says.