Many of this year's athletes are no stranger to the Ironman competition.
Tricia Novak was there cheering on her husband.
"He's done four this will be number five,” said Novak.
But John Ryan was there cheering on a first timer, 50 year old Sarah Carlson.
"Extremely proud of her. Absolutely,” said Ryan.
For Carlson, the competition is about accomplishing a goal she was once told would never be possible.
"This is a huge bucket list goal for me. It's something I've always wanted to do and I never thought I would be able to do," said Carlson.
That's because 11 years ago, Carlson was hit head on by an SUV.
"I lost part of my leg, the tissue, and the biggest injury was my pelvis was crushed into over 40 pieces, I had my knees blown out, my shoulders blown out, and my lower back compressed. I'm lucky to be alive," said Carlson.
After seven surgeries, she was told she may never walk again.
"When the accident first happened and I was told I wouldn't walk my main goal was to be able to walk the kids to school alone and that was my goal and I trained so hard to be able to do that and I did and I took them to school on crutches and that was the biggest accomplishment I've done," said Carlson.
And now, she is competing with some of the top athletes in the world.
"My big motivating force is being a positive role model for my children. I want to show them that when hit with adversity you can persevere and make something good out of anything," said Carlson.