A national day of action against fossil fuel is underway, with hundreds of protesters at Newcastle calling on the federal government to make the switch to renewable energy.
The organiser of the Break Free event, 350.org, said protesters would kayak into the port of Newcastle in an attempt to stop coal ships from moving through the area.
A flotilla of kayaks is due to occupy the water from 11am. Green's Leader Richard Di Natale is expected to make an address at Horseshoe Beach around midday.
The group said one protester had been arrested after occupying the anchor chain of the coal ship Tangerine Island.
NSW police said 4 people had been arrested so far and that an inflatable boat had been seized.
Protester Laura Hogan said she was taking part in the protest to stop the export of coal.
“The need to act is urgent," she said.
"Today we come together as diverse communities of people to demonstrate real leadership and real action. My actions today are driven by my determination to see an immediate shift to a renewable energy future.”
Australian environmentalists are taking part in the protest as a show of global solidarity against fossil fuels.
Civil disobedience is also planned in the United States, UK, Canada, the Philippines and many other nations.
Last month, Fairfax Media reported police expected more that 400 people to sail in to the port on Sunday and that it was "impossible to hire a kayak between Gosford and Port Stephens" ahead of the event.