It’s become an iconic piece of clothing, copied by numerous swimwear lines, written about in fashion bibles like Glamour, outfitted on an official Barbie doll, and even donned memorably (and a little horrifyingly) by Matt Lauer as a Halloween costume on Today last October.

But that red one-piece swimsuit the female stars of Baywatch made so famous in their slow-motion runs along the beach had much more humble beginnings. It was designed to look exactly like the swimsuits worn by real-life California beach lifeguards.

[Photos: Check Out Vintage Beach Pics of the ‘Baywatch’ Cast]

The 1989-2001 series itself was originally conceived to tell the stories of those lifeguards, like Greg Bonann, the Southern California lifeguard and Baywatch co-creator who went to a competition swimsuit company, not a Hollywood costume designer, for the bathing suits that would became the series’ trademark.

“TYR designed the suit per my specs,” Bonann told Yahoo TV. The swimsuits “had to look good on the women, but had to also be functional in the water. The now-famous ‘slo-mo’ shooting … required good support on the top and minimal creep in the back. … All lifeguards, not almost all, but all lifeguards, come from a competitive swimming background. That means that all of these women grew up in one-piece swimsuits, not bikinis.

"The obvious goal was to replicate, as closely as possible, what the actual lifeguard women wear," said Bonann, who wrote Baywatch: Rescued From Prime Time, an official behind-the-scenes look at the series. “When in the water, in big surf, with multiple victims grabbing onto your hair, suit, arms, legs, etc., they could — and do — easily rip off your swim suit if they are desperate enough. A two-piece for women would be just too risky to wear in the water with a victim grabbing, scratching, kicking and screaming.”

[Related: Leonardo DiCaprio: Your Basic ‘Baywatch’ Reject]

Once actresses like Shawn Weatherly, Erika Eleniak, Nicole Eggert, and, most famously, Pamela Anderson put on those customized cuts of TYR red Lycra, the competition swimsuits became something more, something that sealed the show, during its peak, as an international hit that drew more than one billion viewers each week.

And as much as the cast made the swimsuits pop, Bonann and his fellow producers made sure the swimsuits were tailored to each actress. In the one-look-does-not-fit-all Baywatch lineup, a higher neckline was more flattering to Alexandra Paul, who, as Bonann puts it, was more “modestly chested,” and a medium cut worked best for several other cast members. For the series’ breakout star, Anderson, the neckline and armholes were lower and the legs were cut higher at the sides.

All the stars, in other words, were made to look as fetching as possible, wearing as little of the Lycra as possible — while still looking like they could function as lifesavers while rushing into the ocean with their orange rescue cans.

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"There was a clause in our contract that said we couldn’t gain weight," Paul told Esquire. “When I first saw that, I was like, ‘What? I can’t believe this! Why, do they just have these for the women?’ Turns out that it was in everybody’s contract — men and women.

"People would criticize Baywatch for being a fluffy show, and we never pretended to be doing brain surgery,” Paul said. “We were a fluffy show. Everyone else seemed so disappointed and shocked about it — our show did do a lot of good things, especially in places like China or Iran, where people saw women wearing bathing suits and it was OK. To me, in a way, culturally, we did a lot of good. I think people don’t give us credit for that.”

[Related: It’s True: The ‘Baywatch’ Cast Had a Weight Clause]

Anderson, who joined Baywatch in Season 3, left the show after five seasons because she wanted to spend more time with her children, but she has repeatedly called her years in the red swimsuit the best of her career.

Pamela Anderson More

“I loved being active — running in the sand, working out, being in the ocean,” Anderson told Esquire. “A lot of the people that came on to the show before or after me weren’t really comfortable in the ocean, and I grew up on an island, Vancouver Island, and I’d swam in a lot colder ocean than California, so I was like, ‘This is easy! This is great! Are you sure you want to pay me for this?’ I was Baywatch. I was that girl growing up. I was really, really lucky to get that job, and everything else has just kind of been… not as good.”

Anderson has also continued to have fun in the red swimsuit, post-Baywatch.

"I have the red Baywatch swimming costume in my safe. … I put it on once in a while, jump in the shower and rescue my boyfriend,” Anderson, who wore the suit in a 2009 fashion show and in a 2012 Brazilian TV commercial, told Elle. “I have had quite some moments in that suit.”

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Not all cast members were as comfortable with spending their workdays in the swimsuit and the water. Eleniak, who beat out other auditioners like Teri Hatcher and Neve Campbell for a spot in the original series cast, left during the third season, partly because she was unhappy Baywatch had become known more for the red suits than the lifeguard work. Other cast members from later seasons recall how intimidating it was to have to wear The Swimsuit That Pammy Built, sometimes the exact same suit.

"I went and hired a swim coach because I wanted to make sure my form was down," Traci Bingham, who joined the show in Season 7, told Esquire. “They give you this red suit and inside of the suit it says ‘PAM.’ I thought, ‘Oh my god, this is amazing — they’re actually letting me wear one of her suits.’”

[Related: 'Baywatch' Now and Then]

Nicole Eggert, who spent two seasons on Baywatch and participated in a cast reunion on Entertainment Tonight last year, told Esquire in 2012, “It was the biggest mistake I ever made. You’re suddenly being labeled this bimbo and this Baywatch babe, and nobody can act on that show, and it’s a big joke, and it’s number one because of all the T&A. I just was kind of blindsided with it all.”

But Carmen Electra, the show’s second biggest breakout star, has, like Anderson, continued to appreciate the opportunities her little-red-swimsuit days brought her. In 2013, she donned the red one-piece again for an In Touch photo shoot, telling the magazine she had been a little reluctant, at age 40, to wear it. “Once I got it on, I felt amazing. It was a million times better than I thought it would be,” she said. “I feel better than I did at 25!”

BAYWATCH HAWAII, Stacy Kamano, Brande Roderick, Krista Allen, 1999-2001 More

Electra swam the Baywatch waters for just one season — Season 8 — and was one of the final breakout cast members to wear the red suit. For the show’s final two seasons, the action moved off the mainland to become Baywatch Hawaii, where the lifeguards wore yellow swimsuits.

"The lifeguards wear yellow” in Hawaii, says Bonann, who has been certified as a Los Angeles County lifeguard for 45 years. “They also wear yellow in Australia, New Zealand, and parts of Africa. I like to mimic the real lifeguard uniform wherever we set the show.”

Which begs the question, what will be the Baywatch swimsuit color of the future? Bonann confirms to Yahoo TV that both a new TV show and a big-screen movie version of the series are in development.