Katie Ledecky competes in a preliminary heat of the women's 1500m freestyle swimming event at the 2015 FINA World Championships in Kazan on August 3, 2015. (Martin Bureau/AFP/Getty Images)

KAZAN, Russia – There are swims where Katie Ledecky takes dead aim at a world record, and ones where she is merely doing her job, and Monday morning’s preliminary heat in the women’s 1,500-meter freestyle at the FINA World Swimming Championships was to be the latter. Her only mission was to swim a strong race and set herself up for Tuesday night’s finals. The words of her coach, Bruce Gemmell, echoed through her mind: 900 easy, 300 build, 300 choice. Translation: Go easy for the first 900 meters, build through the next 300 and do whatever you want at the end.

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.

The eighth world-record-setting swim of Ledecky’s brief but meteoric career – a time of 15:27.71, about two-thirds of a second faster than her 2014 world record from the Pan Pacific Championships -- was unlike any of the others. It came in the last heat of the last event of the morning preliminaries – three years to the day after the 800-meter win at the London Olympics that propelled her to fame as a 15-year-old -- in front of a sparse crowd at Kazan Arena that nonetheless roared to life as Ledecky closed in on history.

When she touched the wall and looked up at her time – while her fellow competitors, most of them a lap or more behind, mopped up their races – Ledecky, an 18-year-old from Bethesda, broke into a huge grin. She pumped a fist to her family – parents David and Mary Gen, brother Michael and uncle Jon – and when she caught sight of Gemmell in the front row, she raised her hands and shrugged her shoulders, the universal gesture of “oops.”

“I’m in quite a bit of shock right now,” she said moments later. “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.”

Olympic gold medalist Katie Ledecky broke multiple world swimming records before graduating high school. Now in her senior year in Bethesda, Md., she’s wrapping up her high school swimming career and looking forward to World Championships this summer. (Zoeann Murphy/The Washington Post)

Ledecky’s record-setting performance came one day after her gold-medal-winning swim in the 400-meter freestyle, a showing that sparked an examination of the weight of expectations on her, as reporters questioned whether she was disappointed by a time that ranked as the third-best all-time, simply because it was not a world record – and she insisted she was not.

Taken together, perhaps those two races make a point about elite athletes and enormous expectations.

“That’s the great [lesson] I think is true with all sports: When you can relax and not have expectations and let yourself perform at the level you’ve prepared for, sometimes you get your best performances that way,” Gemmell said. ”I would imagine you’d find the same thing from golfers and tennis players and skiers.”

On the second day of an eight-day meet, and with a grueling “double” awaiting her Tuesday night – when she will swim the 1,500-meter final and the 200-meter prelim with only about 20 minutes in between – Ledecky took the “easy” portion of Gemmell’s pre-race instructions to heart. In an event she dominates, with no one in the world within 10 seconds of her this year, she knew she could cruise through the prelims and still finish as the overall top seed.

“I was barely even focusing on this morning’s swim,” she said. “I was just so relaxed.”

As the race began, her kick was visibly reduced from its full power, and she later admitted she was consciously resting her legs and focusing on “pulling” with her arms. But through the first 400 meters, she was 0.16 seconds below her world-record pace, and by the 900-meter mark – the portion of the race she was told to go “easy” – she was a second and a half under it.

She more or less maintained that pace through the next 300 meters – the “build” portion” – with her 1,200-meter split still 1.37 seconds below world record pace. Then came “choice.”

It was around this point that Ledecky caught sight of her family and friends waving her on. What crowd there was on hand began to roar as closed in on history, and the piercing whistle of U.S. national team coach Dave Salo cut through the arena. Ledecky saw and heard it all, and understood. But rather than pushing herself to go hard down the stretch in pursuit of the record, she blocked it out.

“It didn’t even spur me on at all,” she said. “I didn’t want to get up and race even harder because I felt if I just maintained the pace I was holding, maybe I could still get under [the world record]. And if I didn’t, I wasn’t really expecting it anyway.”

Her race was breathtaking in a visceral sense – as her closest competitor, Australia’s Jessica Ashwood, finished a whopping 28.81 seconds and nearly an entire pool-length behind – but it was just as impressive, in a swim-nerd sense, as a model of efficiency and consistency. Throwing out her opening lap of 28.56, when she got a terrific jump and sprinted to the lead, and her closing lap of 29.47, when she knew the record was within her grasp, there was a less than a second’s difference between the fastest (30.53, second lap) and slowest (31.42, fourth) times in the other 28.

Whatever pressure there was on Ledecky here this week – to keep lowering records that seemed unimaginable only a few years ago, before she came along and altered the course of distance-swimming – is off now, at least for the moment. On Tuesday night, Kazan Arena will presumably be packed again, and the ones who missed out on Monday morning’s bit of history will want to see another record.

“In the finals, there’s always more energy and excitement,” Ledecky said. “I’ve never been somebody who’s swum slower at finals, so hopefully I can be right on that [time], or hopefully better.”