She started to train five times a week with local swim team called Oceanus in Aalsmeer.

[4] De Koning broke her first World Record at the Open Danish swimming championships in Esbjerg, March 2006.

She won seven medals at the Championships, of which four golds, one silver and two bronze as well as a new World Record at the 50m backstroke in a time of 45.46 seconds.

A few days later she became World Champion at the 50m freestyle after winning her race in 37.67 seconds to take her third medal of the Championships.

[7] In the final Simmonds managed to improve her time to 1:18.75 while De Koning was only able to swim January 19, 2029 and take the silver, finishing still in front of Paralympic and World Record holder Doramitzi Gonzalez.