2025 World Championships
- July 27 – August 3, 2025 (pool swimming)
- Singapore, Singapore
- World Aquatics Championships Arena
- LCM (50m)
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The semi-finals of the women’s 100m butterfly featured American world record holder Gretchen Walsh and the 22-year-old didn’t disappoint, capturing the top seed in 56.07.
However, Walsh wasn’t alone, as 20-year-old Roos Vanotterdijk of Belgium touched simultaneously, also hitting a mark of 56.07 for a new national record.
Vanotterdijk opened in 26.14 and closed in 29.93 to put up the fastest time of her young career, erasing the 56.66 she logged during the heats of this event here in Singapore.
Entering this competition, however, Vanotterdijk’s national record stood at the 57.05 established at this year’s Swim Open Stockholm in April. That means in a matter of months, the ace has slashed just under a second off her best-ever 100m fly outing.
| Vanotterdijk’s New Belgian Record – 56.07 | Vanotterdijk’s Heats Record – 56.66 | Vanotterdijk’s Old Record – 57.05 |
| 26.14 | 26.12 | 27.14 |
| 29.93 | 30.54 | 29.91 |
Vanotterdijk now ranks as the 9th-fastest woman in history, tied with China’s Liu Zige, with the final yet to come.
Top 10 Women’s LCM 100 Butterfly Performers All-Time
- Gretchen Walsh (USA) – 54.60, 2025
- Sarah Sjostrom (SWE) – 55.48, 2016
- Torri Huske (USA) – 55.52, 2024
- Maggie MacNeil (CAN) – 55.59, 2021
- Zhang Yufei (CHN) – 55.62, 2020 & Regan Smith (USA) – 55.62, 2024
- –
- Emma McKeon (AUS) – 55.72, 2021
- Dana Vollmer (USA) – 55.98, 2012
- Liu Zige (CHN) – 56.07, 2009 & Roos Vanotterdijk (BEL) – 56.07, 2025
- –
But this trajectory is just par for the course for Vanotterdijk who trained under Fred Vergnoux when he was head of the Royal Belgian Swimming Federation before she moved under Mark Faber. Faber replaced Vergnoux in November of last year.
She owns the Belgian national records across the long course 100m free (53.62), 50m back (27.81), 100m back (58.97), 50m fly (25.63), 100m fly (56.07), 200m IM (2:09.73).
Remarkably, all of these new standards have been established in the first half of this year, with the most recent record in the 200m IM set just at last month’s U23 Championships.
Vanotterdijk carries the most entries of all swimmers at these World Championships, slated to race an incredible seven individual races.
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Mark Faber magic! He’s the GOAT of NL and now the Belgian Federation benefits from the KNZB stupidity. Congratulations Roos and all the other Belgian swimmers breaking Belgian National records!!!!
Incredible swim!
incredible versatile swimmer too , Wow !