The courageous Syrian teenager is set to become one of the faces of the Games, having been one of 10 athletes selected to compete for the Refugee Olympic Team (ROT) under the Olympic flag.
The German-based athlete explained at the Olympic Aquatics Stadium how she felt she was living "a dream come true" just 11 months after she plunged into the bitingly cold Aegean Sea to help push a sinking dinghy, overcrowded with 20 migrants, to sanctuary.
Mardini and elder sister Sarah, their home in Damascus having been destroyed in the Syrian conflict, had fled the fighting, trekking through camps in Lebanon. They were seeking, like thousands of other Syrians, to make a new life in Europe by making the treacherous sea crossing in an inadequate boat from Turkey to Greece.
The engine failed in the darkness and the dinghy started taking on water as Mardini, a talented swimmer who had competed for Syria at the 2012 world championships, realised they could all drown. She plunged in with Sarah and two others to push the vessel towards land on the Greek island of Lesbos.
"We were the only four who knew how to swim. I had one hand with the rope attached to the boat as I moved my two legs and one arm. It was three and half hours in cold water. Your body is almost like … done. I don’t know if I can describe that,” Mardini said.
Was that a nightmarish memory? "Not at all. I remember that without swimming I would never be alive maybe because of the story of this boat. It’s a positive memory for me."
The 18-year-old's extraordinary journey finally ended with her reaching Berlin, where she was able to resume her swimming career and was invited to join the Olympic team that she believes will "show the world refugee is not a bad word".
Those in the boat whose lives she helped save will be cheering her on from afar as she competes in the 100m freestyle and 100m butterfly. "They all know that I’m here, they’re always supporting me, saying, 'You deserve it, you're amazing'," she said.
She does not feel like a hero. "Sometimes, it's hard," she said, admitting she was not comfortable being portrayed that way. "But it's amazing to feel like you have been an inspiration for everyone."
Baron Pierre de Coubertin, the founder of the modern Olympics, gave the Games the credo that "the important thing in life is not triumph, but the struggle". Now a remarkable 21st century Olympian has offered her own version.
My message at these Games is just, 'Never give up'.Yusra Mardini Refugee Olympic Athlete