On Thursday, 24 December 1914, an athletic young Hawaiian strode across the beach at Freshwater, a stretch of sand between Manly and Curl Curl. The day was clear and sunny, and Duke Kahanamoku was about to perform a feat never before seen in Australia.

Kahanamoku was 25, a Waikiki beach boy whose "flutter kick" had won him a gold medal for the American team at the 1912 Stockholm Olympics and an invitation from the New South Wales Swimming Association to demonstrate his technique at a meet at the Domain Baths. He was also invited to give a display of...