The 300 kilograms of cocaine seized in Bundaberg, in southeast Queensland, on Friday has a street value of about $120 million and is the fifth-largest cocaine seizure in Australian history, police say.
Four Spanish nationals have been arrested, including a 35-year-old man and a 37-year-old woman who were aboard the yacht.
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Two other Spanish nationals, including a 38-year-old Sydney man - believed to be the ringleader of the group - and a 39-year-old Gold Coast man, were arrested leaving the Port of Bundaberg separately.
They were carrying several suitcases stuffed with cocaine.
Subsequent searches of a Sydney home and a Gold Coast residence have turned up $3 million in cash, with police still counting the money.
Australian Customs had tracked the 16.8m yacht from October 14, when it left Vanuatu, to October 20 when it moored off the Bundaberg coast.
Police monitored the vessel where it sat for three weeks before the Spanish nationals from the Gold Coast and Sydney allegedly travelled to Bundaberg on Friday to take possession of 100kg of cocaine.
The four arrested were expected to appear in Bundaberg Magistrates Court on Monday charged with importing a commercial quantity of drugs.
Customs national manager of enforcement operations Kaylene Zakharoff said the bust highlighted the capabilities of the Australian Federal Police (AFP), customs and Queensland police working together.
"Through this cooperation we've been able to stop nearly $80 million dollars' worth of cocaine hitting the streets which is particularly significant in the lead-up to the party season," she told reporters in Brisbane on Monday.
Police believe the cocaine came from South America and the bulk of it was destined for Sydney.
The drug bust was the result of a nine-month AFP investigation into a money-laundering syndicate, with more arrests expected.
"This is the beginning of the investigation to be honest," AFP national manager for serious and organised crime Kevin Zuccato said.
"We now need to try and find out who are the members of this syndicate and see if we can't do them some further damage down the track."
