During an Amateur Athletic Union (AAU) swim meet, Duke Paoa Kahinu Mokoe Hulikohola Kahanamoku broke the world record in the 100-yard freestyle swim by 4.6 seconds in Honolulu Harbor on August 11, 1911. Officials were so incredulous at his time that the AAU would not recognize his feat until many years later. Duke Kahanamoku swam using a unique combination of an Australian crawl stroke with a flutter kick to add speed.
Known as Duke, or the Duke, he was a three-time Olympic gold medal winner. He broke another record and won a gold medal for the 100-meter freestyle swim at the 1912 Stockholm Olympics where he also won a silver medal in the 200-meter relay event. The 1916 Olympics were not held because of World War I. Kahanamoku broke his own record at the 1920 Olympics in Antwerp, winning gold in both the 100-meter freestyle and as a member of the U.S. 800-meter-relay team. At the 1924 Olympics in Paris, he won a silver medal in the 100-meter freestyle (his brother, Samuel Kahanamoku, won the bronze medal and Johnny Weismuller captured the gold). Kahanamoku also was an alternate member of the U.S. water polo team that won a bronze in the 1932 Los Angeles Olympics.
The Library of Congress has more on Duke Kahanamoku, the Father of Surfing.