Sydney Cavill (1881–1945) was the son of the Swimming professor Frederick Cavill and 220 yards amateur champion of Australia at the age of 16. He is credited as the originator of the butterfly stroke. He followed his famous brothers to America and coached notable swimmers at San Francisco's Olympic Club.
The Cavill Family from Australia was inducted as Honour Swimmers in 1967 in the International Marathon Swimming Hall of Fame and in the International Swimming Hall of Fame. The Cavill Family consists of two generations of six colorful champion swimmers (1897 – 1938) who promoted swimming and set national and regional records including Frederick Cavill, Ernest Cavill, Charles Cavill, Percy Cavill, Arthur Cavill, Sydney Cavill and Dick Cavill.