Gwangju - Britain's Adam Peaty promised to go even faster after shattering his own 100 metres breaststroke world record on Sunday.
The Olympic champion stormed home to win his semi-final in a time of 56.88 seconds, becoming the first swimmer to break 57 seconds and eclipsing his previous mark by just over two tenths.
"There's no other word except for incredible. I've been chasing that for three years now," said the 24-year-old.
"Ever since I touched that wall in Rio, I knew I could go faster," he added.
"It always comes down to where and when you do it and what kind of season you've had."
"(In the final) hopefully we can go a little faster. It's still the semi-final. It'd be embarrassing not to come away with the world title but you know I don't think like that."
Peaty has not been beaten for five years over 100 metres breaststroke in major competition and he never looked in any danger in the second men's semi-final on day one in Gwangju.
The tattooed pin-up, chasing a hat-trick of world doubles in the 50m and 100m, went out strong, turning 0.12 inside world record pace as fellow Briton James Wilby struggled to keep up.
Peaty punched the air after the roar of the crowd told him he had finally broken the magical 57-second barrier.
"I said I wasn't going to chase 56," he said. "I'd let it come to me and that's exactly what we've done.
"I've learnt that the most important asset is my mental health. If I'm chasing 56, it's unhealthy."
But Peaty insisted his main focus was on Monday's final.
"The process in my head is tomorrow anyone can beat me," he said.
"I think that's the place you've got to be, because if I go into that race thinking I'm the world record holder I won't be achieving the best possible version of myself," he added.
"I've come here to win a world title and that's still my main focus, so this was just a bonus and I'll use this energy tomorrow."
Wilby and Japan's Yasuhiro Koseki finished two seconds behind the peerless Peaty in an almost embarrassingly lopsided race.
China's Yan Zibei won the first semi-final in 58.67 to qualify second behind Peaty for the final.
Title holder Peaty will also battle it out for the 50m breaststroke crown later in the week.
"I think I've evolved so much in these last three years," he said.
"I'm not an angry teenager anymore."