AUSTIN, Texas (AP) Katie Ledecky swam the eighth-fastest 400-meter freestyle in long-course history just 45 minutes after posting a personal best in winning the 100 free at the Arena Pro Swim Series on Thursday night.
The 17-year-old Olympic champion from Bethesda, Maryland, was ahead of her world-record pace at the halfway mark in the 400 before finishing in 4 minutes, 0.47 seconds - 8 1/2 seconds ahead of Hungary's Katinka Hosszu, FINA's 2014 World Swimmer of the Year.
''I was pretty surprised when I touched the wall, because it didn't feel really fast,'' she said.
Ledecky opened the finals session with her 100 victory in 54.55. Hosszu was second in 54.66. She had a personal best in the in the 100 qualifying at 54.89 and then crushed that in the finals.
''I always love to get up and race the 100, especially when it's my first event. You feel really fresh and ready to go,'' Ledecky said. ''I definitely exceeded my expectations in the 100 against a tough field.''
America's top two 100 freestyle swimmers, Missy Franklin and Simone Manuel, are competing this week.
Ledecky, a Maryland high school senior, holds the world record in the 800 and 1,500 freestylesl. The 800 is Saturday, the final day of the meet at the University of Texas Lee & Jones Texas Swimming Center.
Olympic gold medalist Nathan Adrian of Bremerton, Washington, won the men's 100 in 49.11.
Olympian Micah Lawrence of Pflugerville, Texas, took the women's 200 breaststroke in 2:25.75, and Josh Prenot of Santa Monica, California, won the men's race in 2:12.17.
Olympian Connor Jaeger of Fair Haven, New Jersey, won the men's 400 in 3:47.58.
In the 100 butterfly races, Canada's Noemie Thomas won the women's race in 58.57, and Jack Conger of Rockville, Maryland, and the University of Texas, topped the men's field in 51.64.
Ryan Lochte, who has 11 Olympic medals, was fourth in the 100 butterfly, but did not make the finals in the 100 free.
The competition is the second stop in the series formerly known as the Arena Grand Prix Series.