The teenager made it to the final in a 14th of a second, knocking him into a driveway far away.

No one was watching Ahmed Hafnawi in the 8th lane of the Olympic swimming pool, but all eyes were on the Tunisian teenager at the end.

Hafnaoui was the amazing champion of the 400m freestyle at the Tokyo Olympics on Sunday, beating a group of faster and older swimmers.

The 18-year-old completed the game in 3 minutes and 43.26 seconds, reverberating loudly in the almost empty 15,000-seat arena, marking his victory.

He is the slowest qualifier to reach the finals.

“When I touched the wall, I believed it, I saw myself first,” he said. “I was so surprised.”

Jack McLaughlin of Australia won the silver medal, and the American Kieran Smith won the bronze medal. After eight laps, the gap between the top three was less than one second.

“When I got into the water, I was just thinking about medals, not time,” Hafnaoui said.

He made it to the final with 14/14 seconds, knocking him into the far lane. The fastest qualifier was in the middle of the pool and Hafnaoui could not be tracked during the game.

When asked how much he knew about Hafnaoui, Smith said, “Not at all.”

Hafnaoui has another chance to surprise in the 800m freestyle on Thursday [Jonathan Nackstrand/AFP]

Hafnaoui joined Ous Mellouli, becoming the only Tunisian to win a gold medal in swimming.

Meluli won the 1500m freestyle at the 2008 Beijing Olympics, one of three Olympic medals in his career.

The teenager trained in the capital Tunisia is the fourth Olympic gold medalist in this North African country. He is the second youngest athlete in the African country to win a gold medal in swimming.

Standing on the podium, his coach waving his arms triumphantly in the stands was an overwhelming moment for Hafnaoui.

“I shed tears because when I saw my country’s flag and heard the national anthem in the background, it was great,” he said. “I am very proud of it. I dedicate it to all Tunisian people.”