Guillaume has always been keen on water sports, he started to compete in Optimist in Le Havre at the age of 8. The next step is obvious: 420, then 470. A World Youth Champion title in 470, 2 World Vice-Champion titles in 420 and several European Champion titles in 420 and 470.

Halfway between Olympic sailing and ocean racing, Guillaume competed in Diam24 on several Tour Voile (formerly Tour de France à la Voile). The results are very positive: 2 podiums and a victory in 2019.

In 2020, Guillaume has been chosen to join the Norman Skipper scheme for 3 seasons in Figaro. He will learn one season with Alexis Loison, taking part in all the double-handed races, before single-handed racing during the 2022 season. He finished 2nd in the Solitaire du Figaro, and entered the very exclusive circle of Bizuths to climb on the podium.

2023 will be Guillaume's last Figaro season with the Normandy Region.