Gretchen Walsh won her first individual long course world title by clocking 54.73 seconds in the 100m butterfly at the World Swimming Championships.
She nearly broke her own world record of 54.60 seconds set on May 3.
What happened?
Gretchen Walsh prevailed over Belgian Roos Vanotterdijk and Australian Alexandria Perkins.
The margin of 1.11 seconds was the second-largest in event history.
Gretchen Walsh owns the top eight times in history.
Why it matters for Gretchen Walsh
This win adds to her stacked resume: four Olympic medals and 11 world records.
Gretchen Walsh has seven gold medals at the world short course championships.
She has nine individual NCAA titles in four years at Virginia.
What comes next?
Gretchen Walsh still has the 50m fly and 50m and 100m frees left.
She may also have relay duty.
Gretchen Walsh was affected by acute gastroenteritis like most of the US swim team.
But she said "that swim took a lot of guts" and she's "really proud" of the result.
Gretchen Walsh was aiming for a 55-second finish but went under with a 54.73-second swim.
The World Swimming Championships are being held in Singapore.
Gretchen Walsh made the US team for worlds in four individual events.
She is a medal contender in all of them.
The championships will run for eight days.
Gretchen Walsh's win secured the US's first gold medal on the second day of the meet.