Louis Marchant started diving at the age of eight, and as a teenager soon established himself as one of the leading divers in Britain. At the age of 15, he finished ninth in the 1931 Amateur Diving Association (ADA) Plain Diving Championship, a title he won the following year. In 1934, when 18, he was selected for the British Empire Games at London, and won a bronze medal, in an England 1-2-3, in the platform diving event. A London, Surrey and Southern Counties champion, Marchant won his first ASA title in 1934, when he won the National Graceful Diving title. Between 1946-50 he was the National Plain Diving champion five years in succession. Marchant won a second major international bronze medal, at the 1947 European Championships in Monte Carlo, but failed to add to his collection at the London Olympics the following year, when he could finish only 11th.