In an Olympic preliminary heat, Katie Ledecky posted the eighth-fasted time in the history of women's 800-meter freestyle.

She's incomparable.

Ledecky's 8:12.86 prelim swim on Thursday afternoon set an Olympic record. And it honestly looked like she was barely trying. She blasted the rest of her heat, a heat that posted the four fastest times of the four heats run on Thursday. Ledecky outpaced second-place finisher Boglarka Kapas of Hungary by almost seven seconds.

Ledecky owns the world record in 800-meter freestyle. She's broken her own record four times in the past three years. It currently stands at 8:06.68; Ledecky set the record in Austin, Texas, in January. She is expected to break that record when she swims in the final.

When she won the gold in this event in 2012 in London, as a 15-year-old, she touched the wall in 8:14.63. Such a swim now would be considered a disappointment for Ledecky, who's well on her way to becoming the greatest freestyle swimmer ever.

Another American -- Leah Smith -- qualified for Thursday night's semis with an 8:21.43 swim.