Protesters in kayaks, dinghies and sailboats have blockaded the world's largest coal port, calling on the federal government to stop new fossil fuel projects.
The flotilla succesfully prevented ships from leaving or entering Newcastle Port on Saturday, with the protest planned to continue for 30 hours ending on Sunday.
Greens leader Adam Bandt joined protesters as part of the Rising Tide movement's action.
Mr Bandt led calls for the government to end new coal and gas projects, adopt a 75 per cent emissions reduction target and stop coal exports from Newcastle.
"In the middle of the climate crisis Labor is making the problem worse by opening more coal and gas mines," he said.
Climate Change Minister Chris Bowen decried the Greens' action and pointed to his government's new investments in batteries for wind and solar farms.
"While the Greens are protesting, we are progressing jobs growth and emissions reductions by developing offshore wind," he told AAP on Friday.
NSW Minerals Council chief executive Stephen Galilee denounced the protesters as "extremists".
Newcastle Port contributes to roughly two per cent of the world's global coal supply and its exports generate billions in royalties for the state government.
A spokesperson for the Port said due to safety concerns shipping had been halted.
"At present, due to the number of people currently in the shipping channel, all shipping movements have ceased due to safety concerns, irrespective of the cargo they are carrying or intend to load," they said.
Mr Galilee said the disruption would not change global coal demand or supply but would have a major impact on the NSW economy.
Mr Bandt said governments and corporations cared more about money than the safety of Australian communities.
"People are fed up because Labor is not listening and now people are making their voices heard," he said.
During the 2022 election, Labor positioned itself as the more environmentally friendly of the two major parties, committing to net-zero emissions by 2050.
To achieve this, the nation needs to reduce its greenhouse gas output by 43 per cent within the next decade.
But since entering office, Environment Minister Tanya Plibersek has approved four new coal projects that would produce an estimated 147 million tonnes of emissions across their lifetimes, according to the Australia Institute.
Another 25 coal mines are also waiting on federal government approval, which would bring the total potential emissions up to 12.8 billion tonnes.
Retired public health professor Peter Sainsbury said immediate action was needed to save the world.
"Climate change far exceeds any public health threat that I have seen in my 40 years as a public health doctor," he said.
The blockade is the latest in a string of climate protests ahead of the 2023 United Nations Climate Change Conference, which opens in Dubai on Thursday.
Mr Bowen and assistant minister Jenny McAllister will attend the conference.
