Carter qualified for three Olympics in 1972, 1976 and 1980; his best result was fourth place as a member of the British men's team in the 4×100-metre medley relay in 1976. As a British relay team member, he won bronze medals in the 4x100-metre medley relay at the 1975 World Aquatics Championships and 1977 European Aquatics Championships. He also won a silver medal in the 1500-metre freestyle at the 1974 European Aquatics Championships. At the ASA National British Championships he won the 1973 and 1974 1500 metres freestyle titles, the 200 metres backstroke titles in 1976 and 1977, the 200 metres medley title in 1976 and the 400 metres medley title in 1974.