Olympic champ Katie Ledecky swims year's fastest 400 free

Olympic champion Katie Ledecky opened her season by winning the 400-meter freestyle at a Pro Swim Series meet with the fastest time in the world this year.

She touched in 4 minutes, 1.01 seconds — over 6 seconds clear of the field Thursday night.

Ledecky won the 400 free at the Rio Olympics last summer, one of five medals she earned. She is finishing her freshman year at Stanford.

Nathan Adrian won the 100 free in 48.18, second-quickest in the world this year. He won the event at the 2012 Olympics and took bronze in Rio.