John Dumaresq was the first Australian-born officer to command the Australian fleet. He was born on 26 October 1873 at Rose Bay in Sydney but his family moved to England when Dumaresq was just two.

Dumaresq joined the Royal Navy as a cadet in 1886, aged 13. He was commissioned as a lieutenant in 1894 and served with the Channel Fleet. In 1904 he was promoted to commander and, having taken an interest in torpedo work earlier in his career, was attached to the Admiralty to supervise the equipment of torpedo vessels. Dumaresq was keenly interested in the science of naval warfare and he invented a rangefinder that greatly improved the accuracy of naval gunnery.

In 1907 Dumaresq married Christian Dalrymple and the following year he commanded the torpedo flotilla when it escorted King Edward VII on a visit to Russia. After his return, Dumaresq commanded two of the Home Fleet's torpedo destroyers. Promoted to captain in 1910, he invented several fire-control devices that were used in the First World War.

Dumaresq commanded the Shannon, a light cruiser, in the battle of Jutland in 1916. During this action he conceived the idea of launching aircraft from a ship's deck. In February 1917 he was transferred to the RAN as captain of HMAS Sydney and later in the year he took command of the British vessel Repulse, which he captained in a successful battle against the German flagship, Königsberg. Dumaresq returned to Sydney in December 1917. To his great pleasure the admiralty had agreed to the installation of an aircraft-launching platform on Sydney, the first to be fitted to a ship. The first flight was a success and the device offered ships some protection against zeppelins and land-based aircraft.

Dumaresq remained in command of Sydney until the end of February 1919. The following month he was given command of the Australian fleet with the rank of commodore. In June 1921 he was promoted to rear admiral, becoming the first Australian-born officer to attain that rank and to command the Navy.

By the early 1920s, cutbacks in defence spending led Dumaresq into conflict with senior political figures as he sought to ensure that the Navy was properly resourced. He returned to the Royal Navy on 29 April 1922, thus ending his service with the RAN. Dumaresq's final gesture, criticising Australia's apathy towards defence spending, suggests something of his willingness to publicly state his views on matters of national importance. Some regarded him as a strict disciplinarian but he was widely respected, shy of publicity, and has been credited with introducing an esprit de corps into the Navy that the young service had been lacking.

Dumaresq never reached England to take up his new appointment. He fell ill on the voyage and died of pneumonia in the Philippines on 22 July 1922.