“This was absolutely surreal and amazing,” Dana Vollmer said after winning the 100-meter butterfly. (MARK RALSTON/AFP/GETTY IMAGES)

For a decade, U.S. swimmer Dana Vollmer hung around, never quite emerging, never quite going away. She overcame a heart condition, shoulder tendinitis and back injury, but she could not surpass the very best athletes in her events. She earned a reputation as a reliable relay team member, but not a star, or even a star-in-the-making. She didn’t even qualify for the 2008 Olympic team.

Yet she became the first American to collect a gold medal at the swimming world championships here Monday, righting Team USA’s world by toppling a field in the 100-meter butterfly that included the world record holder and defending world champion.

Vollmer, 23, quite literally rode a wave — actually, a bunch of ocean waves in a new training regimen — to her first major individual title. On a night fellow American Ariana Kukors collected a bronze medal in the 200 individual medley and Michael Phelps and Ryan Lochte easily advanced to the men’s 200 freestyle final, Vollmer, finally, stepped to the top of a medal podium all by herself.

“This was absolutely surreal and amazing,” Vollmer said. “To finally win in my favorite event, and to feel like I did it individually . . . It’s so empowering, so exciting . . . It kind of felt like I was always second . . . Being on all of the relays, and never really being the top shot.”

Vollmer’s performance here has not only been surprising, it’s also been emphatic and convincing. She won Monday in 56.87 seconds, beating Aussie Alicia Coutts (56.94) and China’s Lu Ying (57.06). The time she swam in the preliminaries (56.47) was the fourth-best ever and fastest by a woman not wearing one of the speed suits that were banned in 2009, going under Dutch legend Inge de Bruijn’s 56.61 from 2000.

Early in a meet widely expected to validate the truly skilled and fit swimmers while exposing the pretenders — those who got special enhancement from the speedsuits that led to 43 world records at the ’09 championships — Vollmer has emerged as a legitimate star. She is within sight of Sarah Sjoestroem’s plastic-suit world record of 56.06.

“I feel like the suits now let more of an athlete’s ability show rather than the technology making the athlete,” said Vollmer, who won an Olympic gold in the 4x200 freestyle relay in 2004.

As Vollmer stepped up in textile, Kukors proved she could perform in both kinds of material. The defending world champion and reigning world-record holder in the 200 medley, Kukors considered her performance against a strong field a victory of sorts — at least, in perception. She finished in 2 minutes 9.12 seconds, behind China’s Ye Shiwen (2:08.90) and the versatile Coutts (2:09.00).

“I really felt like I needed to prove myself, after 2009, of not just being a ‘suit swimmer,’ ” said Kukors, who swam a 2:06.15 in a speedsuit. “I’m really proud of that time.”

Vollmer said the extra buoyancy the suits added actually proved burdensome. A natural floater who had emphasized core strength under her coach Teri McKeever, Vollmer said she actually feels sleeker and faster in textile. That feeling has been enhanced as she’s dived into novel training; she has traveled to Fiji and Australia in recent months to work with ocean guru Milt Nelms, who prescribed drills that involve swimming into waves, alongside them, and with them, a practice designed to build strength while encouraging perfect technique.

The workouts have not only helped her stroke, Vollmer said, but they’ve also enhanced her enthusiasm. After pondering retirement when a string of injuries contributed to her failure to make the 2008 Olympic team cut, Vollmer felt rejuvenated.

Even so, the physical problems that have dogged her for years never quite ceased. She noticed last fall she would become easily fatigued in practice, and she did not know why. Nutritionist Anita Nall, the former swimming star who trained at the North Baltimore Aquatic Club, ran blood tests and confirmed that Vollmer had a host of food allergies, including to eggs and gluten. She recommended dramatic changes to Vollmer’s diet. Gradually, her strength returned.

But the ailment had taken its toll. She hadn’t been able to train adequately at any distance beyond a sprint. She increased her already significant dependence on ocean swims, dry-land training, dance classes and pilates as a substitute for endless pool workouts. The reduced workload led McKeever to pull Vollmer out of the 200 freestyle here, but it also seemed to enhance her sprints – namely, the 100 fly — and direct her focus.

“I do love the sport,” Vollmer said. “I just didn’t like how I was doing it before.”

Vollmer, who plans to marry former Stanford swimmer Andy Grant Aug. 20, arrived in Shanghai feeling great.

With the 100 freestyle left to swim, she is certain to leave feeling even better.

“That’s part of being seasoned,” McKeever said. “This has been a decade now that she’s been at the national level. She’s had ups and downs. Getting through the disappointment of not making Beijing and getting through that, it lets you know you can get through things.”