Maritime NZ's area of jurisdiction just got 50 million square kilometres bigger.

The organisation is now responsible for issuing maritime warnings in an area in the south-west Pacific Ocean, between New Zealand and South America, covering 50 million square kilometres.

Previously, Land Information New Zealand was the ocean warning co-ordinator and Maritime NZ looked after coastal warnings, but one organisation being responsible for both makes life safer for mariners, Maritime NZ chief executive Keith Manch says.

"Warnings will include alerting them to hazards such as dangerous wrecks, large unwieldy tows in congested waters, newly discovered rocks and reefs, changes or damage to lights and beacons, and weather," he said.

Hydrography and mapping of the sea and coast will still be done by LINZ.

Maritime NZ's work will be carried out at the Rescue Co-ordination Centre and Maritime Radio Service, both based in Lower Hutt.