spring tides, that water level being below the bench mark. The tidal range for spring tides in the bay was . The survey of Cairns Harbour in 1878 was part of an ongoing process of surveying the Queensland coastline and its harbours and rivers. In 1770 Captain James Cook in HM Bark Endeavour was the first British navigator to chart the coast of what is now Queensland, and he visited and named Trinity Bay. Admiralty surveys commenced after the establishment of the British Admiralty Hydrographic Office in 1795. Queensland's waters were charted and surveyed by navigators including Matthew Flinders (1799 in the schooner Norfolk; 1802 in ; Lieutenant Charles Jeffreys (1816-17 in HM Brig Kangaroo); Lieutenant Phillip Parker King (1819–21, HM Cutter Mermaid and ); Lieutenant John Oxley (1823, HM Cutter Mermaid); Captain Henry J Rous (1827, HMS Rainbow); John Clements Wickham (1839, ); John Lort Stokes (1841, HMS Beagle); Captain FP Blackwood and Lieutenant CB Yule (1843–45, and HM Cutter Bramble); Captain Owen Stanley (1847–48, ); and Captain HM Denham (1858–61, ). After Queensland's separation from New South Wales in 1859, more accurate charts were required as the new colony developed its ports. Coastal shipping was of vital importance to Queensland's economy prior to World War II, given the size of the state, the lack of all-weather roads, and delays in completing the coastal rail link from Brisbane to Cairns. In 1860-61 Queensland entered into an agreement with the British Admiralty to split the annual costs of hydrographic surveying (then about per annum). The Admiralty would provide staff and instruments and publish charts, while the Queensland Government would provide the lodging, subsistence and "means of locomotion" for staff. The focus was on charting a safe shipping route along the Queensland coast, but the Admiralty surveyors could also assist the Queensland Government with its river and harbour surveys. In 1861 Lieutenant (later Commander) George Poynter Heath, RN, was appointed as marine surveyor to Queensland's Surveyor-General's Department, and in his first year he surveyed the Maroochy and Mooloolah rivers in . In 1862 he was appointed Portmaster and Marine Surveyor of Queensland. That same year Master James Jeffery was appointed as Queensland's first Admiralty Surveyor. He hired a local vessel to survey the Great Sandy Strait, Hervey Bay, and the mouth of the Mary River, but soon persuaded the Queensland Government to have a surveying schooner constructed. , a vessel built