How it unfolded
Katie Ledecky was 19, and had already won the 200m and 400m freestyle and the 4x200m relay at Rio. In the 800m freestyle final, she led from the first 50 metres, and for nearly 15 minutes afterward, no one had her in sight. Her pace barely changed. Ledecky's method wasn't to surge early and hang on, but to hold a tempo from start to finish that no one else could sustain. She broke her own world record again, finishing in 8:04.79. Britain's Jazz Carlin took silver in 8:16.17 and Hungary's Boglarka Kapas bronze in 8:16.37. The winning margin was 11.38 seconds, close to 20 metres of open water. At Rio, Ledecky won four golds and a silver overall, and also set a world record of 3:56.46 in the 400m freestyle. No one but Ledecky herself came close to this 800m mark for the next nine years.
Why it still matters
This race shows that dominance in swimming doesn't only take the form of a hundredth-of-a-second finish. Ledecky went on to win the 800m freestyle at four straight Games through Rio, Tokyo and Paris, a record no swimming event had ever seen. The baseline for women's distance swimming was redrawn this night, and every middle- and long-distance swimmer since has designed their own pacing against Ledecky's split sheet.