The beach was emblazoned with a clear message that was visible from above on October 7: the words “Stop Adani”.

The words were spelt out as part of a national day of action opposing the proposed Carmichael coal mine.

The message was repeated across the country as more than 16,000 activists formed human protest signs.

The protests stretched Australia-wide at more than 45 locations, including Bondi Beach, the Whitsundays, Perth’s Cottesloe Beach and Port Douglas.

In Newcastle more than 600 people donned red and hit the sand to express their opposition.

The gathering also had speeches and musical performances as hundreds clutched anti-coal signs.

“The Adani coal mine would fuel climate change, bringing more frequent and intense storms and bushfires,” Naomi Hodgson, an organiser of the Newcastle event, said.

“It is madness to open the Adani mega coal mine at a time Australia needs to be transitioning away from coal.”

The national day of opposition came as a new poll found the coal mine – and a proposed $1 billion government-funded loan – was lagging in public support.

Adani has promised thousands of local jobs but opponents say the project will fuel global warming and destroy the Great Barrier Reef.

Research commissioned by The Australia Institute found 30 per cent of Australians supported Adani's plans for the mine, which is backed by both sides of politics at federal and state levels.

Conversely, 44 per cent of voters opposed the project, including 49 per cent of Labor voters and 29 per cent of Coalition voters.

After being told there were concerns about Adani's corporate track record and environmental impact, 55.5 per cent of voters said they opposed the project.

Only 26.1 per cent said they supported it, according to the ReachTel poll of 2194 Australians taken in October.