More than 65 people were arrested or given court attendance notices after “lock on” protests at the port’s coal loaders and the coal rail bridge onto Kooragang Island, but the blockade itself was peaceful.

Port authorities worked the shipping schedule so that no coal ships – or any other cargo vessels – moved in or out of the port during the blockade, which ran from late morning to late afternoon.

Horseshoe Beach was packed with participants – mostly wearing red – and supporters, watched from the water by a flotilla of police in boats and on jet skis.

Musicians including Midnight Oil’s Rob Hirst and Australian blues singer Ash Grunwald performed on the harbour from the renewable-powered catamaran Gaia’s Dream. A fleet of about  200 catamarans and kayaks moved constantly across the water, taking protesters out for stints on an almost glassy harbour.

Organised by climate group 350.org in concert with other environmental groups and activists, the Horseshoe Beach protest doubled as an election campaign launch site for The Greens, with Senator Richard Di Natale saying it was time Australia got serious about “tackling dangerous global warming”.

Sunday’s protest was one of at least 18 around the world scheduled this month under the #breakfree2016 banner as part of a fortnight of “escalated action to keep coal, oil and gas in the ground”.

Protesters last blockaded the port in October 2014, when the Pacific Climate Warriors – who returned to Newcastle on Sunday – were joined by about 100 canoes on a day that saw the waterborne flotilla stare down a bulk carrier exiting the port.

Sunday’s protest was effectively twice as large, and by late afternoon the arrest list totalled 66, with Newcastle police commander Superintendent John Gralton saying some demonstrators had “set out to break the law and put themselves and others at risk”.

Organisers defended the actions of those arrested, saying people were determined to take action having “seen our governments repeatedly refuse to act on climate change”.

Greens MLC Jeremy Buckingham said coal had lost its “social licence”.