Their proud parents, meanwhile, were part of a record-breaking indoor swim meet crowd, taking it all in.
For the Shackells, Father's Day weekend and the first day of the U.S. Olympic trials started perfectly.
Aaron Shackell became the first American to qualify for the Paris Games by winning his race with a time of 3 minutes, 45.46 seconds — just minutes after his sister qualified for the women's 100 butterfly final on Sunday night.
"I think a lot of people get nervous when they look at 20,000 people in a stadium and I think for me, it makes me go fast," Aaron Shackel said. "I've always dreamed of performing in a basketball arena, a football stadium and swimming, you know, hasn't always had the opportunity to put on a show in front of 20,000. It's everything to me."
Shackell knows the Lucas Oil Stadium story well. He lives and trained for the trials in near by Carmel, Indiana, a northern suburb of Indianapolis.
It's the venue the NFL's Indianapolis Colts call home, the venue that hosted the 2021 men's Final Four, the venue that hosted the 2022 college football national championship game and this year's NBA All-Star Saturday night. And now the first football stadium to host the trials will also be known as the place where a graduate of Carmel's perennial powerhouse swim program became the first American to qualify for the Paris Games.
The 20,689 people in the crowd and his sister roared with approval.
"My mom is probably crying," Alex Shackell said. "He has all these interesting celebrations, so I knew he would do something."
The Shackells certainly know swimming.
Their father, Nick, was an All-American at Auburn who competed for England in the 1996 Olympics. Their mother, Ali, also was an All-American swimmer at Auburn. This week, all three of their children are among the 1,007 swimmers competing in this nine-day meet.
But few expected this, even after Aaron Shackell opted to take a redshirt year at California to focus on making his first Olympic Team.
"I trusted (Carmel coach) Chris (Plumb), and I knew if I came back (here), I would improve in some way," Shackell said. "And if I didn't make it, that was OK. I knew I did everything I could so I just really had to get my head around that."
He edged out Kieran Smith by three-tenths of a second. Smith was a member of the American Olympic team in Tokyo, and now kit gives the Shackells something else to contemplate.
By finishing second in her heat with a team of 56.78 seconds, Alex Shackell was slower than only three other swimmers in the two semifinal heats — Olympic favorites Torri Huske and new world-record holder Gretchen Walsh and Regan Smith.
First, though, she made sure sure she didn't miss seeing her brother's first race.
"I went down to the warm-up pool and they wanted to drug test me," she said. "I asked if I could watch my brother."
What she saw was pretty much what she and her family expected.
"She was always better than me," Aaron Shackell said. "She was the first one to hug me after I got downstairs. I felt like she was more excited that I made the team than with her own event, but she's excited because she taught me."