Katie Ledecky's swims -- even events that are finals, the ones for the medals -- have become as must-watch as anything at this year's Games in Rio.

On Monday night, the 19-year-old sensation swam in the second semifinal heat of the 200-meter freestyle. Predictably, and practically effortlessly, Ledecky touched well in time to qualify for Tuesday night's final. Her time: 1:54.81. Surprisingly, it wasn't good enough for first. Ledecky was out-touched by the woman who might be the second-best female swimmer in the world, Sweden's Sarah Sjostrom, who won the heat with a time of 1:54.65.

"I have some things in my head that I can work on for tomorrow night, and hopefully I can put it all together," Ledecky said on NBC of her second-place finish.

The only other swimmer in Ledecky and Sjostrom's class, Italy's Federica Pellegrini, had the third-fastest time of the night (1:55.42). They'll all battle in the pool on Tuesday night, all swimming in the three closest lanes to each other. If Ledecky wins, it will be her third medal in as many events in Rio, and her second gold.

"I have tomorrow morning off and I can some good sleep in and be ready for tomorrow night," Ledecky said.

The other American swimmer of note in the 200-meter women's freestyle semi on Monday: Missy Franklin. She was the star of 2012 Games in London, having taken home four gold medals. But her time in the 200 free is done. Franklin had the slowest time of all 16 swimmers in the semifinal heats (1:57.56).

It's not a place we're accustomed to seeing Franklin finish. But her Rio trip isn't over yet: she still has the 200-meter backstroke, plus she'll compete in the 800-meter freestyle relay.

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Katie Ledecky cruises in the 200m freestyle semis, will swim on Tuesday. Getty Images