Zirk, 25, came 22nd in the same event at summer's Paris Olympics and was seventh in the 200-meter butterfly final at the same games.

In Incheon, he put in a time of 3:42.99, securing the sixth-fastest qualifying time, on Thursday morning. It was his ninth-fastest recorded time in this event.

Zirk described his morning swim as "Quite a fast preliminary swim."

"I had to push to make sure I went through, but I didn't swim myself empty, and I can definitely go faster than that."

"I need to start more boldly in the first half of the distance and stick with the quick guys for as long as possible. I think it will be quite a fast final again," he went on.

The qualifying heats winner was reigning world champion Kieran Smith (U.S.) with a time of 3:39.15.

Zirk's compatriot Ralf Tribuntsov narrowly missed making the men's 50-meter freestyle final, finishing ninth with a time of 21.53, just 0.13 seconds shy of securing a place. The time was close to his PB and domestic record of 21.22, set last year.

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