Officers boarded the Australian fishing vessel, the Coralynne, about 150 nautical miles off the east coast on Saturday morning as part of a joint investigation by the Australian Federal Police, NSW Police and Australian Border Force.

In three-metre seas, the officers found three men on the boat and a fire in the cargo hold - along with what is believed to be the largest amount of cocaine uncovered in an Australian bust since 2017.

The men were arrested and charged with attempting to import a commercial quantity of border-controlled drugs.

Hong Kong national Man Wan Chan, 40 and Australian men Christopher Preca, 32, and Jackson Giles-Adams, 27, faced Sydney's Central Local Court on Monday where they were refused bail.

Police raided homes in Chatswood, Zetland and Glenbrook on Monday as part of the investigation.

The men will face court again on October 14, with the possibility of a maximum sentence of life in prison if convicted.

Police and the Border Force began their investigation last week after intelligence from New Zealand authorities that a vessel had been spotted heading towards Australia in an unusual fashion.

Police allege officers saw the foreign vessel transfer the drugs to the Coralynne off the coast of Newcastle on Saturday.

AFP Assistant Commissioner Justine Gough told reporters on Tuesday the exact amount cocaine was still being calculated, but it was estimated to be in the hundreds of kilograms and could be as much as one tonne - worth between $100 million and $250 million on the street.

Assistant Commissioner Gough said the authorities would continue to "reduce the misery caused by illegal drugs to the Australian community".

"Even though we're going through a global pandemic, organised crime groups continue to attempt to exploit our borders, supply chains and exploit consumers to make criminal profits," she said.

NSW Police State Crime Commander Assistant Commissioner Stuart Smith said the boarding operation was "high risk" and took place in swell in excess of three metres.

He said the arrests should serve as a warning to people involved in organised crime.

ABF Regional Commander for NSW Danielle Yannopoulos said the operation led to a haul that was "likely to be the biggest cocaine detection since 2017".

"Australia's maritime border is vast and criminals think they can exploit that and evade detection, but they are wrong," she said.

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