On 12 January 1929, Kavanaugh was swimming at Bondi Beach approximately from the shore when fourteen-year-old Colin Stewart was attacked by a shark and dragged underwater. The shark inflicted severe wounds to Stewart's side and hip, and Kavanaugh—who was located only a few metres away—immediately swam to his assistance. The shark made a second pass at Stewart as Kavanaugh neared. Securing a hold on Stewart, Kavanaugh struggled towards the shore. As the pair neared, they were assisted by two other men who dragged Stewart ashore, where he received medical attention before being rushed to hospital. Stewart subsequently died of his injuries the following morning.
