Somerville was a Canadian golfer and all-around athlete. While at Ridley he excelled in all sports. In 1919 he led he football team to victories with his consistent punting and faultless catching. In 1920 he captained a superb team. At cricket, he was the first Canadian schoolboy to score a double century. He was consistently top of the bowling averages in 1919, 1920 and 1921. Sandy was also the recipient of the Mason Gold Medal in 1921. His athletic career continued after he left the school; he won six Canadian Amateur Championship golf titles between 1926 and 1937, and in 1932 became the first Canadian to win the U.S. Amateur. He was selected by the Canadian Press as Canada's athlete of the year for 1932, and in 1950 was picked as Canada's top golfer of the first half of the 20th Century. While at the University of Toronto, Somerville played for three years for the Varsity Blues football team and Varsity Blues men's ice hockey team (1921–24). He was also one of Canada's top cricket players. Later, Somerville won three Canadian senior golf titles and served as president of the Royal Canadian Golf Association in 1957. He was inducted into Canada's Sports Hall of Fame (1955), the Canadian Olympic Hall of Fame (1985), the Canadian Golf Hall of Fame (1971), and the U of T Sports Hall of Fame (1987). He died at age 88 in 1991. The London Hunt Club, Somerville's home course for most of his life, has a room in its clubhouse honouring Somerville's golf achievements.