David Collet was educated at Oundle School before going to Pembroke College, Cambridge. He proved himself to be an excellent rower, and in 1921 reached the final of the Colquhoun Sculls, losing to fellow Pembroke student K. N. Craig. The following spring, Collet won his rowing Blue, and went on two win two more, in 1923 and 1924. He was also secretary of the Cambridge University Boat Club. Collet rowed at the Henley Royal Regatta several times, and was runner-up in the Grand Challenge Cup in 1923 when Pembroke, making their début in the final, were beaten by Leander.
Collet returned to serious sculling and won the Wingfield Sculls three years in succession, 1927-29. He was hoping to win the Centenary race in 1930, but was beaten in the final by Denis Guye. In 1928 Collet won a bronze medal in the single sculls at the Amsterdam Olympics, and was granted the Freedom of the City of London that year. He went to live in Arizona, USA, in the mid-1930s but returned to Britain at the outbreak of World War II and served as a lieutenant in the Royal Navy, based at Plymouth. Collet returned to the United States after the War, and died there in 1984.
Great Britain