Japan's Ippei Watanabe broke the men's 200 metres breaststroke world record on Sunday by becoming the first swimmer to go under two minutes, seven seconds.
The 19-year-old clocked a time of 2:06.67 at the Kosuke Kitajima Cup in Tokyo, eclipsing the previous best set by countryman Akihiro Yamaguchi in 2012 by 0.34 seconds.
"I'm stunned," Watanabe told reporters after lowering a record once regularly broken by Japanese swim great Kitajima, who was watching on at Tatsumi pool.
"It still hasn't sunk in. I'm unbelievably happy. I just tried to go for it but I didn't think I'd get (the record)."
Watanabe threatened a sensational shock at last year's Rio Olympics with a Games record going into the final, only to finish sixth.
"This is a marker," said Watanabe, looking ahead to this year's Budapest world championships in July.
"I'll be looking to win the world title and to keep improving the world record."