New York ? When you’re packing your beach (or pool) bag, leave the stained T-shirt and fraying shorts at home. Pick out your best beach ensemble instead.

Don’t have a beach “ensemble” yet? It’s time to get one, says Joe Zee, editor in chief of Vitals, a fashion magazine that alternates its focus on men and women each month.

“If you really look at the way fashion designers have approached swimwear, it’s as clothing,” Zee observes.

The trend started at the highest level at companies like Chanel almost a decade ago, and it’s now moved into the mainstream. Almost every spring-summer collection, ranging from designer runways to discount retailers, now features coordinated cover-ups, tote bags and bejeweled flip-flops that leave those white plastic thongs from boardwalk vendors in the dust – or, more accurately, in the sand.

“Men and women have really made an effort to wear beachwear in their everyday life. This way you can run into lunch wearing a tunic or dress, or hit the stores. You don’t have to go home and get changed. It’s not unacceptable to be out in your beachwear; it’s been part of the European culture for so long, and now it’s happening here. … You can be chic and elegant in your swimsuit,” Zee says.

Accessories designer Kate Spade hasn’t made the full leap into a ready-to-wear collection yet, but she partnered with the edgy apparel team As Four to create nine core items that are intended to be adaptable to time and place. And the As Fourkatespade garments make ideal cover-ups: A knife-pleated, green-apple chiffon piece, for instance, could be a wrap skirt, a bandeau or a capelet, and one side of a reversible shrunken shirt is made of water-absorbent terry cloth.

“I love dressing for the beach, and I always do. It’s just as easy to throw a bright beachy shift dress on as it is an old T-shirt, especially if you are not feeling so great in a bathing suit,” Spade says.

The right cover-up can give you extra confidence and add “a little skip to your step” because you won’t be worried about what body part is exposed or if you’ve struck a flattering pose, she says.

Even children are targets for the total look, says Jasmin Coyle, merchandise manager for The Disney Store. “It’s event dressing, sort of like Halloween. A vacation or even a day at the beach is important in the lives of kids,” Coyle says.

It’s also big business, adds Disney Store president Mario Ciampi. It’s a category that’s exploded, with sales now five times what they were two years ago.

Most kids’ styles in stores feature bright colors, complementary patterns (such as florals and stripes in the same colors), flashy trim and practical shapes that stay on in the water but are easy to get off.

The same can’t be said for adult beachwear.

As Four teamed with Kate Spade to create pieces that can be adapted according to the occasion, including a day at the beach.

“You can’t go swimming in half these suits; a lot are for the body language,” Zee says.

Hot trends include graphic cuts with banding and striping, intricately-designed one-pieces and high-waisted bikinis. “There’s a whole nod to retro, old Hollywood and Hitchcock heroines going on in fashion, and it’s trickled to swimwear. It’s innocent but beautiful. … It’s not just a triangle string bikini that’s sexy anymore.”

To complete the outfit, try a loose jacket – maybe in linen – or baggy jeans, or the more traditional tunic or sarong. It OK if they have beading or embroidery and even appear a bit fancy. “Women are even wearing jewelry to the beach,” Zee notes.

Men tend to choose their beach wardrobe more by their own personality than trend.

“Men are either a Speedo guy or a board-short guy. … But they might be trying brighter colors or floral prints. They’ve become more adventurous than the navy blue suit,” Zee says. “Abercrombie (& Fitch) capitalized on the frat boy surfer look with brights, neons, florals, and it’s being accepted by these guys.”

In fact, board shorts, which sit low and are loose through the leg, are Zee’s favorite item of the season. “It works for men and women, and it’s more flattering in the end.”