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Even when Katie Ledecky has her foot off the gas, she cannot help but be great.

The 18-year-old Maryland native broke her own world record in the women's 1,500-meter freestyle Monday, doing so despite the race being a preliminary heat at the FINA World Swimming Championships in Kazan, Russia.

“I’m in quite a bit of shock right now,” Ledecky said, per Dave Sheinin of the Washington Post. “It’s probably one of the coolest world records I’ve broken. Each one is really unique, but just sort of how relaxed I was and how calm. I think breaking that record is just testament to the work I’ve put in and the shape I’m in right now.”

Ledecky finished her swim in 15:27.71, more than a half-second better than the record she set last year at the Pan Pacific Championships in Phoenix. Her time was 26.52 seconds better than Lotte Friis, who came in second place during the heats. Friis' mark was closer to ninth place than it was to Ledecky's, the massive favorite for a gold medal.

Making the record all the more impressive was that Ledecky wasn't even attempting to swim her best time. Outside of a disqualification, it was all but a given that she would qualify for Tuesday's final. She and coach Bruce Gemmell had actually implemented a breezy game plan—right until the moment everyone knew a world record was at stake, per Sheinin:

As the race unfolded, she couldn’t see what everyone else in the pool could: her lap times flashing on the scoreboard, each 50-meter split keeping her well ahead of her own world-record pace. But towards the end, when she turned her head to breathe, she could glimpse her family and friends in the stands, and they were all waving sideways with both hands – “Go! Go! Go!–a gesture she understood immediately.

Ledecky is largely seen as the next great hope for American swimming. She won her first Olympic gold medal at the 2012 Summer Games at age 15 in London, becoming the second-youngest Team USA swimmer to win the sport's top honor (77 days older than Beth Botsford, who won gold in 1996). Now only growing better with age, Ledecky and Missy Franklin, 20, should be Team USA's two anchors at the 2016 Games in Rio de Janeiro.

Until then, though, Ledecky will merely have to settle for sleepwalking her way to the world record books.

Follow Tyler Conway (@tylerconway22) on Twitter.