Britain's Adam Peaty broke the men's 50m breaststroke world record for the second time in just a few hours on Tuesday by clocking 25.95 seconds in the semi-finals.
The 22-year-old had broken his own record, set at the 2015 world championships in Kazan, when he swam 26.10secs in the morning's heats, with the final to come on Wednesday.
"This morning prepared me to do a world record again, it was just me easing through the stroke, touching the wall, progressing to the semi-final," said Peaty.
"It was the same tonight, I was on such a massive high from this morning.
"I've learned from the experience that I've had the last two years.
"I came in tonight, I actually thought I'd go slower as I was a little less energetic, but tomorrow's the day to do it."
Having won the 100m breaststroke gold on Monday, Peaty showed his blistering form over the shorter distance by breaking the 26-second barrier.
The scorching time left his rivals in his wake as Brazil's Felipe Lima was 0.73secs back, while South Africa's Cameron van der Burgh was third fastest into the final at 0.79.
"It's impressive eh, he's the first one in history (to go under 26 seconds)," said Van der Burgh.
"He's a legend, it's a privilege to watch such amazing swimming in my lifetime."
However, Lima insisted Peaty will not have everything his own way on Wednesday.
"It's insane, but the final will be another race," said the Brazilian.
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