Nonetheless, organizers from the 350.Org environmental group said it underscored concerns that the burning of coal mined in Australia was having devastating effects in the South Pacific.

The action at the entrance to the Port of Newcastle briefly interrupted ships heading to open waters under a police marine escort. But it failed to bring any coal vessels to a halt. Newcastle handles more than 4,000 ship movements annually, more than 90 percent loaded with coal from the nearby mines of BHP Billiton, Rio Tinto, Glencore and others.

"We are not willing to drown because of climate change. We are trying to change the narrative from 'we are drowning' to 'we are not drowning, we are fighting,'" said George Nacewa, an activist from Fiji.

The burning of coal and other fossil fuels has contributed to climate change, they said, which causes sea level rise. That, environmentalists added, poses an existential threat to residents of low-lying areas around the world, especially in the Pacific, where entire island countries could disappear.

Environmental activists teamed up with Pacific islanders in eastern Australia on Friday in an attempt to block the world's largest coal export terminal by forming a blockade of canoes, surfboards and kayaks.

Scientists say that climate change will cause rising sea levels and higher tides, which will swamp lower-lying Pacific islands and lead to more severe weather and storms.

Sea levels are expected to rise by at least seven feet by the end of the century, according to an assessment by NASA and University of California researchers, who discovered that a massive ice sheet in Western Antarctica was melting at an "unstoppable" rate.

Calling themselves the Pacific Climate Warriors, the demonstrators on Friday chanted Methodist hymns before boarding traditional canoes to block shipping lanes leading from the port. They were joined by others on surfboards and kayaks. The flotilla was soon flanked by police on jet skis and in motorboats as a tanker was shepherded out to sea by three tugboats. There were no arrests.

Milan Loeak, a 26-year-old from the Marshall Islands and daughter of Marshall Islands President Chris Loeak, said her islands were already feeling the impacts. Earlier this year, the largest king tides in memory swamped the capital, Majuro, in the southern atolls while a severe drought plagued the north — leading Loeak to declare a state of emergency.

"I've seen my people and my islands suffer the impacts of climate change through droughts and floods from high tides," said Loeak.

Ahead of the United Nations Climate Summit in September, Loeak released a video message warning his fellow heads of state that the effects of climate change already experienced in the Marshall Islands was just a preview of the disasters the rest of the world could expect if significant action was not taken.

In the video, Loeak stood in front of the sea wall he built to protect his family's home from being inundated by the rising seas.

Australia, which relies on coal-fired power stations for electricity, has the world's highest carbon emissions per capita. Tens of thousands of workers are employed in collieries and whole towns rely on mines for their livelihood.

Australia's conservative government in July repealed a tax that had forced around 300 of the country's biggest emitters to pay for their CO2 emissions. Australian Prime Minister Tony Abbott, opening a new BHP coal mine last week, declared coal was "good for humanity" and vital to the world.

"We are a rich country and should be putting more money into renewable energies," said Meg Leathart, an Australian attending the protest. "Tony Abbott is pulling us back 50 to 100 years."

Al Jazeera and Reuters