Special Olympics athlete Chris Nikic crossed the finish line on Saturday to become the first person with Down syndrome to complete an Ironman triathlon.

Guiness World Records recognized Nikic's achievement after he finished a 3.8-kilometre swim, a 180-kilometre bike ride and a 42-marathon run at the Ironman Florida competition in Panama City Beach.

"Ironman. Goal set and achieve," said Nikic in a post to Instagram. "Time to set a new and Bigger Goal for 2021."

Nikic completed the race in 16 hours 46 minutes and 9 seconds -- 14 minutes under the 17-hour cutoff time.

Nikic fell off his bike and was attacked by ants at a nutrition stop, but he pushed on to finish the competition, the Special Olympics said in a release.

"We are beyond inspired, and your accomplishment is a defining moment in Ironman history that can never be taken away from you," the Ironman Triathlon organization said in a post to Twitter.

The organization documented the historic race with a series of updates to social media on the day of the competition. The final two miles of Nikic's run were streamed live on Ironman's Facebook page.

Nikic and his father Nik developed the "1 percent better challenge" to stay motivated during training. The idea is to promote Down syndrome awareness while achieving 1% improvement each day, according to Nikic's website.

"To Chris, this race was more than just a finish line and celebration of victory," Nik Nikic said. "Ironman has served as his platform to become one step closer to his goal of living a life of inclusion and leadership."

Nikic's accomplishment earned him congratulatory messages from celebrities, such as tennis great Billie Jean King and runner Kara Goucher, and people around the world, including 33,000 new followers on social media, according to Nikic.

After his record-setting achievement, Nikic will focus on competing in the 2022 Special Olympics USA Games and continuing to raise money for Special Olympics, Down syndrome and RODS (Racing for Orphans with Down Syndrome) through his platform.

"I achieved my goal and now I want to help others like me," he wrote to Instagram.