At the Olympic Games in Antwerp in 1920, he was selected by the National Olympic Committee of Belgium, to speak the first athlete in the history of the written by Pierre de Coubertin Olympic oath.
Boin participated in four Olympic Games in part (1908, 1912, 1920 and 1924). In 1908 he won the Belgian water polo team the silver medal four years later he won the bronze medal. At the 1920 Summer Olympics he was a member of the Belgian Degen team that won the silver medal.
After his playing career Boin remained the sport as an official. Between 1955 and 1965 he held the office of President of the National Olympic Committee of Belgium.