Three decades after capturing her first Olympic gold in Atlanta, Brooke Bennett is still chasing medals—just in a different arena. The three-time gold medalist, now 46, was recently spotted training at Sand Key Park in Clearwater, preparing for a challenge that pushes even the fittest athletes to their limits.

"I did not want it to fully control my life or fully sacrifice everything," Bennett says. "I've lived that life."

This weekend in Jacksonville, Bennett aims to complete her first full-distance IRONMAN triathlon—a grueling 2.4-mile swim, 112-mile bike ride, and 26.2-mile run. At her age, she has 17 hours to finish. But for Bennett, this isn't about winning. It's about proving something to herself.

"I am not doing this to be No. 1. To be the best. I do it for me. I do it for others," she says.

Known as "the Mermaid" for her dominance in the pool, Bennett is now showing the world she has legs too. "Everybody knows me as the Mermaid, and I'm just the Mermaid tail. Nobody I think ever visualized legs," she jokes.

As a mother of two, Bennett's Olympic fire still burns, but her life and body have changed. "Some days, I honestly surprised myself because I thought I needed 26 hours in the day to make this happen," she admits.

Early 4 a.m. wake-up calls and a disciplined schedule have kept her on track. "To be 46 and to run more than I've ever run in my life—when I did my 18-mile training run, I was like, 'Holy Cow, I really did it.' It was not pretty, it was not fast, but I'm not doing it to run fast."

Fewer than 0.01% of the world's population has completed a full-distance IRONMAN. The number of those who also own multiple Olympic gold medals is even smaller. If anyone deserves to hear the words "You are an IRONMAN," it's Brooke Bennett.