BUDAPEST, Hungary (AP) Matt Grevers wasn't sure what was going on. He wasn't alone.
One of swimming's newest - and certainly craziest - events was on display Wednesday at the world championships, where the United States set a pair of world records while winning the 4x100 mixed medley relay.
Grevers led things off by swimming the backstroke, giving the Americans a slight lead, but breaststroker Lilly King - competing against seven men, including Britain's world-record holder Adam Peaty - was only in fifth place when she passed off to teammate Caeleb Dressel.
''When Caeleb was in the water, I had no idea who's winning the race,'' Grevers said. ''I don't know if we're ahead or behind. I don't know how it's all going to balance out, how much of a lead Simone (Manuel, swimming the freestyle anchor) is going to need. It's just chaos.''
It worked out just fine for the Americans.
Dressel, swimming against only one other man, pushed the U.S. to a commanding lead. Manuel cruised to victory, touching in a time of 3 minutes, 38.56 seconds.
That easily eclipsed the mark of 3:40.28 put up by an entirely different U.S. foursome - Ryan Murphy, Kevin Cordes, Kelsi Worrell and Mallory Comerford - in the morning preliminaries.
''It's really cool that we had two relays that would've won tonight,'' Grevers said.
Australia took the silver, while Canada and China tied for the bronze.
Governing body FINA added two mixed relays to its program at the 2015 world championships in Kazan, Russia, also debuting the 4x100 mixed freestyle relay.
While scorned by swimming traditionalists, the athletes seem to enjoy the uniqueness of men and women competing in the same events.
The International Olympic Committee clearly saw the appeal, approving the 4x100 mixed medley relay for the 2020 Tokyo Games.
''It's interesting to watch,'' Grevers said. ''You're not sure who's winning, even when one team is real far ahead. It's uncharted territory, which is really fun, because as swimmers we usually know what's going on.''
The mixed events have forced both athletes and coaches to address a whole new set of strategic challenges. For the athletes, especially the women, it's the adjustment of swimming in very choppy water when the competitor in the next lane is far ahead. For the coaches, it's deciding on the fastest combination of two men and two women in four different strokes.
Given the depth of its talent, the U.S. will be an overwhelming favorite when the mixed medley relay makes its Olympic debut.
Grevers and his teammates already are eyeing the chance to claim another medal.
''It's tough to get on this team. It's tough to get on the relays,'' he said. ''It's definitely a huge motivation.''
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