Police have arrested and charged 11 climate protesters after they breached an exclusion zone that covered most of Newcastle harbour during the Rising Tide people’s blockade.

Thousands of people have flocked to the annual climate protest at the world’s largest coal port. On Saturday, hundreds of protesters, including the Australian Greens leader Larissa Waters, paddled out in kayaks.

The NSW government has put an exclusion zone over most of the harbour until 7am Monday with protesters who breach the zone, which is marked by buoys, facing enforcement action.

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NSW police said that as of 1:30pm Saturday 11 people had been arrested and charged with alleged marine-related offences “as a high-visibility police operation continues in Newcastle”.

“The police operation is ongoing, and more information will be provided when it becomes available,” a spokesperson said.

Rising Tide said in a statement 19 people had been arrested with some released without charge, but police did not confirm the larger number.

Australian Greens leader Larissa Waters (centre) takes part in the Rising Tide people’s blockade in Newcastle on Saturday. Photograph: Darren Pateman/AAP

The climate activist organisation said the arrests were made as kayakers, a small boat and swimmers entered the shipping channel leading into Newcastle harbour, to prevent the passage of a coal ship.

They said 10 swimmers had been pulled from the water by police as they swam across the channel. They said four kayakers who entered the channel from the Stockton side, opposite Horseshoe beach, were also arrested. They said a further five people – including members of the Knitting Nannas – were arrested after they entered the shipping channel on a small boat, but the Knitting Nannas were among those released without charge.

“As a result of the protest, NSW police lost control of the channel, and a coal ship named Cemtex Leader scheduled to enter the harbour was forced to turn around,” Rising Tide said in a statement.

Protesters attend Rising Tide’s blockade in Newcastle on Saturday. Photograph: Darren Pateman/EPA

The group said some people had been charged for entering a marine exclusion zone, a charge which carries a maximum of $1100 fine. They said others had been charged under anti-protest laws that carry a maximum penalty of two year’s imprisonment.

Jonathon Dykyj is a Newcastle parent and one of the swimmers who entered the channel.

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“The personal consequences to me of getting arrested today pale into insignificance compared to the consequences that runaway climate change will have on our community, our lives and the lives of our children,” he said.

“The Albanese government is failing the working families of the Hunter Valley by not protecting us from climate damage, and not planning for a just transition for coal workers.”

Jonathon Dykyj: ‘The personal consequences to me of getting arrested today pale into insignificance compared to the consequences that runaway climate change will have on our community.’ Photograph: Rising Tide

A video posted to Waters’s Instagram shows the Greens leader paddling in a kayak alongside other protesters.

“We are part of a flotilla of thousands of good-hearted people fighting for a safe climate and I could not be more proud to be out here on the water with them,” Waters said in the video.