After failing to qualify for the 2008 Olympic Games, Dana Vollmer started the 2012 London Games with a splash as the American took home the gold medal and set a world record in the 100-meter butterfly on Sunday night.

The 24-year-old from Syracuse, N.Y. was third at the turn, but roared back after the first 50 meters. Vollmer finished with a time of 55.98 seconds, breaking the record set by Sweden's Sarah Sjostrom of 56.06. Sjostrom set the record while using a high-tech bodysuit at the 2009 World Championships, which are now banned. 

The effort by Vollmer wasn't completely surprising. She almost broke Sjostrom's record at the U.S. Olympic trials in June.

Vollmer swam half the record-setting race without her swimming cap.

"The top cap came off," said Vollmer. "I have never had that happen before. I thought about it, and maybe it kept my mind off my legs hurting or something. I don't know. It's just so exciting, the whole thing." 

In 2004, Vollmer qualified for the Olympics as a 16-year-old in 2004 and was part of the gold-medal winning 4×200-meter freestyle relay squad that set the world record. She failed to make the 2008 team in Beijing after being slowed by health issues, which put her swimming career in jeopardy.

Vollmer's rebound from 2008 makes her success on Sunday one of the top stories of the London Games.

"I'm on top of the world right now." she said. "I still know I can go faster."