Taught to sail at a young age by his father, Durward Knowles’ first major success in the Star Class on the international scene came in 1946, when he won a bronze medal alongside Basil Kelly at that year’s World Championships. The following year, with Sloane Farrington, he took gold and was selected for his first of eight Olympic teams. In 1948 he represented Great Britain and came in fourth with Farrington but, from 1952 on, Knowles represented the Bahamas. In 1952 he and Farrington were fifth, but they earned their first medal, bronze, in 1956, which became the nation’s first Olympic medal. Farrington remained with Knowles through 1960, when they placed sixth, and then retired in favor of Cecil Cooke. At the 1964 Games, Knowles and Cooke won Bahamas’ first Olympic gold medal, its last medal of any color until 1992, and its last Olympic title until 2000.
Knowles competed with his stepbrother Percy in 1968 and Montague Higgs in 1972, placing fifth and thirteenth respectively. When he made a surprise return at the 1988 Games, with Steven Kelly, he became one of only four Olympians at the time to have competed in eight editions of the Games (the others were Danish sailor Paul Elvstrøm - for whom Seoul was also his eighth Olympics - and Italian equestrians Piero and Raimondo D’Inzeo). He also one of only four Olympians at that time to have competed over a span of 40 years (the others were Elvstrøm - who also accomplished this feat in Seoul - Norwegian sailor Magnus Konow, and Danish fencer Ivan Osiier). Knowles was the oldest competitor at the Games, carried the Bahamian flag in the Opening Ceremony, and finished 19th with a partner who had not even been born when Knowles had taken part in his first two Olympics.
In addition to his Olympic accomplishments, Knowles also took silver at the 1954 World Championships, with Farrington, gold at the 1959 Pan-American Games, again with Farrington, and bronze at the 1974 Worlds, with non-Olympian Gerald Ford. Knowles received the Olympic Order in Silver in 1989 and was knighted in 1996 for his accomplishments. Upon the death of Sándor Tarics in May 2016, Knowles became the oldest living Olympic champion.