Marchand crushed American Ryan Lochte's 14-year-old world record.
The time 1.52.69 was a new record with 1.31 seconds.
I knew I would be close to my personal record, because it felt good in the trials, but over a second. 1.52 is completely crazy. I'm so happy, says Marchand whose personal record before was 1.54.06.
The 23-year-old Frenchman became a national hero last year when he at the Olympic Games on home ground swept home four gold medals.
For the World Championship in Singapore, he chose to put aside 200 meters breaststroke and 200 meters butterfly and go all in for 200 and 400 meters medley.
It was probably the right decision, he says in the stadium interview and is met with the audience's cheers in the WCH Arena.
Outside the arena, a storm was brewing with rain, thunder and lightning.
There was certainly a lot of lightning around Marchand. On his first day of competition in the World Championship and already in the semifinal.
With a more pleasant competition schedule, he showed that there are world records in his body.
In Paris, just the world record was what was missing in the joy.
Now I just want to think through everything and process it. It's just an explosion of joy, he says.
Twelve-year-old Chinese prodigy Yu Zidi is ready for her second World Championship final in Singapore after taking the eighth and last final ticket on 200 meters butterfly. Earlier in the week, she finished fourth on 200 meters medley.
