The international swimming community, gathered here for the FINA World Championships, got a one-day respite from the tasks of recalibrating its record book and getting its collective head around the phenomenon in its midst. Katie Ledecky swam again Thursday, for the fifth day in a row, but this time was all giggles and hugs and goofy smiles as she and three teammates swam off with the gold medal in the women’s 4x200 freestyle relay, Ledecky’s fourth of this meet.

“We had a blast out there,” said Ledecky, the 18-year-old from Bethesda. “It was so much fun being in the ready room with those girls, just so relaxed.”

On Friday, the pursuit of history begins again, with the preliminary heats of the women’s 800-meter freestyle, one of three events in which Ledecky holds the world record.

The finals are Saturday, and if she wins — and no one in the world is within 10 seconds of her this year — she will complete an unprecedented sweep of the 200, 400, 800 and 1,500 freestyles at a single world championship.

It is a feat that has no official name, but one that may henceforth be known as the “Ledecky Slam.”

Katie Ledecky broke her own world record in the womens' 1500-meter freestyle at the world swimming championships in Kazan, Russia. Thirty minutes later, she was back in the pool again to qualify for the 200 meter freestyle final. (Jayne W. Orenstein/The Washington Post)

Like everyone at Kazan Arena, Frank Busch has struggled to process what he has witnessed this week out of Ledecky. As the national team director for USA Swimming, Busch has helped nurture Ledecky’s meteoric career. As the head of the U.S. delegation, he has had a front-row seat for her stunning triumphs here.

As a longtime coach and swimming historian with nearly 50 years in the sport, he knows swimming has never witnessed anything like her.

“I’ve never seen anything quite like this,” Busch said Thursday. “And I’ve seen a lot of stuff. I’ve seen Michael [Phelps] win eight gold medals [at the 2008 Olympics], [but] this is just a different thing. . . . She’s doing things that are unprecedented in our sport.”

Those things are worth recapping: A gold medal on Sunday in the 400-meter freestyle, with a time that ranked as the third-best all-time. A world record in the preliminaries of the 1,500 free on Monday, when she barely even used her legs.

Another world record in the finals of that race on Tuesday, followed just 30 minutes later by a 200 free semifinal in which she passed four rivals in the final 50 meters to narrowly earn a berth. Finally, on Wednesday, a victory over a stellar field in the 200 free, an event she has only begun to race seriously in the past 12 months.

The 200 free she swam Thursday, in the anchor leg of a relay that also included Missy Franklin, Leah Smith and Katie McLaughlin, appeared completely free of pressure, particularly after McLaughlin closed hard over her final 50 meters and delivered to Ledecky a nearly dead-even race.

“I knew I’d bring it home,” Ledecky said, “and get this thing done.”

A year from the 2016 Rio de Janeiro Olympics, she is sparking debate over whether she is already — before even starting college or obtaining a driver’s license — the best distance swimmer, or the best freestyler, or both, in history.

“What she does is incredible,” said Franklin, who finished third to Ledecky in Wednesday’s 200 free final, then joined her on the medal stand following Thursday’s relay win. “And it’s never been done before.”

But because this is swimming, with its long history of doping scandals, it was only a matter of time before those debates about her also came to include thinly veiled accusations of doping.

On Wednesday, German television station ZDF aired unsubstantiated accusations about Ledecky from a pair of on-site swimming analysts, one of whom said, in German, that he was “more than suspicious” about her, and the other of whom said he had spoken to other swimmers and “there is no one who isn’t more than suspicious.”

The analysts later interviewed Ledecky briefly on the pool deck and asked her about “questions” being raised in regards to her feats, particularly her 1,500/200 double on Tuesday.

“I trained for it,” she answered. “I worked hard for it.”

Indeed, Ledecky’s in-season training regimen is legendary in U.S. swimming circles for both its volume and intensity — nine sessions per week of between 5,500 and 8,000 meters, plus several dry-land workouts.

Her rise since emerging as a 15-year-old phenom in 2012, as well as the corresponding drops in her times, have been steady and logical, with no sharp spikes that would suggest doping.

Ledecky is believed to be the most drug-tested swimmer in the sport, since, by FINA bylaw, every world record automatically triggers a drug test beyond the standard in-competition ones administered randomly.

She has set seven world record since June 2014, more than any other swimmer in that time. Through Wednesday, she had been tested at least four times since arriving in Kazan, including once before the competition.

“Katie’s not on anything. She doesn’t even know how to spell drugs,” Busch said Thursday. “It’s not part of what she does. But all of our sports across the world are tainted by — as soon as one person does it, and then someone [else] does something out of the ordinary, immediately they want to make a connection. And that’s unfortunate.

“In Katie’s case she’s just been given a gift. There are athletes all over the world who have great gifts and don’t take them to the next level. So you really appreciate people who will take it to the next level. . . . Great accomplishments just don’t happen all that often in history. We’re just watching history, so enjoy it.”