Throughout the war the defence of the country’s harbours was ever in the mind of the Government. This saw the establishment of a Yachtsman’s Naval Defence Force, a motor boat section of the Motor Service Corps, an Examination Service and an attempt to develop an aerial maritime reconnaissance capability.
When the necessity to deal with German mines laid off the coast arose a small organisation had to be developed, the requisite equipment found and the expertise learned. This home-grown force was able to satisfactorily sweep the two minefields laid by the raider SMS Wolf such that when a check sweep was made by Royal Navy minesweepers after the war, no further mines were swept.
During World War One the main source of fuel for ships of all types was coal and there was a need to ensure a regular supply of coal for the ships of the fleet, in all corners of the globe. The mines of Westport produced some of the best coal for maritime use which was in demand by the Admiralty and also the Commonwealth Naval Board for the Royal Australian Navy. So much coal was exported for naval usage that there was a severe shortage of coal for domestic use in New Zealand during the years 1917-19.