Lap after lap, Melissa Stockwell churns, ignoring fatigue. But her physical sacrifice is nothing new. Stockwell lost a leg in Baghdad for her country.
"We went under the underpass and there was a big explosion - a big boom," Stockwell told CBS News correspondent Mark Strassmann.
In April 2004, Lt. Stockwell was on a routine patrol when an improvised explosive device ripped through her Army humvee. Blood poured from one leg.
"It didn't register that it was gone," she said. "So I said, 'I'm hurt, I think something happened to my leg.' "
Four years later, though, something wondrous happened to her life. As a swimmer, she's one of the first two Iraq veterans to make the U.S. Paralympic team, which starts competition Saturday in Beijing.
The other is Scott Winkler, a medal favorite in the shotput.
Five years ago, Winkler had a freak accident in Iraq. He fell of an ammo truck, his body grotesquely twisted. He was left paralyzed below the chest.
Winkler practices on his own front lawn. The shot put became his therapy - both physical and mental.
Six months after his very first throw, he set a world record.
"I look at it as this is my battle. This is where I do my battle," Winkler said. "It's a competition and I'm there to win."
Stockwell's success is just as improbable. After her amputation, she discovered swimming. And a new mission outlined on her new leg as a reminder of her goal - Beijing gold.
"Immediately I knew I wanted to try it," she said.
When Melissa started training in January, she was a long shot to make the team. By April, she had already set an American record in the 400-m freestyle. She was on her way to Beijing to compete.
They're soldier-athletes on a new battlefield.
"The Army slogan was 'be all that you can be,' so I guess that comes into play," said Stockwell.
"I cannot let my country down. I will not let my country down," said Winkler.
In Beijing, Stockwell will compete in three swimming events. And these new combat buddies will cheer each other on.
"The way she swims, I mean she swims like a dolphin," Winkler said. "Real quick."
"I think I'll be extra proud when I hear how he does," said Stockwell. "Just, we come from the same place."
And they ended up in the same place - wearing their country's uniform again, with medals in sight.