Still just 17, she has all the attributes to be the next big thing, and not just in the pool.
Her prodigious talent has long been the talk of the swimming world with the only question whether she could translate it to the biggest stage of all -- a pressure-cooker stadium with 15,000 screaming fans at the Paris Olympics.
McIntosh answered that emphatically in the 400m medley on Monday, powering to the wall in 4mins 27.71secs, putting more than six seconds between her and her nearest rival.
It followed a sensational 400m freestyle swim on the opening day of action at La Defense Arena, outgunning American great Katie Ledecky for silver behind only Australian Ariarne Titmus, who is unbeaten over the distance since 2019.
More Paris gold is there for the taking, with McIntosh favourite in the 200m medley and a serious contender in the 200m butterfly.
Her journey to the top began at the pandemic-delayed Tokyo 2020 Olympics, where she made her mark as a 14-year-old by coming fourth in the 200m freestyle behind winner Titmus.
"The Tokyo Olympics were way harder mentally, being pretty young back then, but at the same time having no one in the stands for obvious reasons, and it was actually my first senior international meet ever," she said.
"Learning to manage that was definitely something that took a lot of practice, but now having everyone in the stands and feeding off the energy of the crowd makes the race go by much faster and makes it easier."
Nobody in her family or entourage is surprised by her rise to the top.
"We knew even at seven or eight years old that she was going to be an exceptional swimmer... beating 10 and 12-year-old swimmers by a pool length," her father Greg McIntosh told AFP ahead of the Games.
"She is a force of nature. She has been since she was a child."
Very competitive
McIntosh is already a four-time gold medallist at the world championships -– in the 200m butterfly and 400m medley in 2022 in Budapest and in 2023 in Fukuoka.
And last May, she broke her own world record in the 400m medley, in front of a hometown crowd during the Canadian Olympic trials.
For the past two years, the star has trained in Florida, spending six days a week in the pool, starting at 4:00am
"All of her time is devoted to swimming," said her sister Brooke McIntosh, speaking from the family home in the Toronto suburb of Etobicoke.
The McIntosh family's passion for sport runs deep: their mother Jill competed in the 1984 Los Angeles Olympics and older sister Brooke is a top pairs figure skater.
"We're very competitive. This is really in our blood," said Brooke.
With two teenagers with high-level sporting careers, the McIntoshes have split the family in two: Summer and Jill live in the United States for pool training, Brooke and Greg in Canada for ice training.
Despite the hype and the eyes of the world watching her, Summer said she said was just "trying to make team Canada proud".
"I just hope I try to inspire as many young kids as possible and I hope that they know that," she added after her proud moment on top of the podium on Monday. "If I can do it, they can do it too.
"I was once in their shoes watching the Rio Olympics. And now that I'm here eight years later."
