New Zealand authorities have intercepted 3.2 tonnes of cocaine that was found floating adrift in the Pacific Ocean.

Operation Hydros was a joint effort by police, customs and the NZ Defence Force. In a joint media conference today, the authorities said the drugs have a street value of "half a billion dollars".

In total, 81 bales of cocaine have now made the journey back to New Zealand aboard the Royal New Zealand Navy vessel HMNZS Manawanui after being discovered six-days-ago. The drugs have now been destroyed.

Some of the bales had stickers to identify them, including a Batman logo and a four leaf clover.

Police Commissioner Andrew Coster says the large size of the shipment means it was likely headed for the Australian market.

New Zealand authorities have intercepted 3.2 tonnes of cocaine that was found floating adrift in the Pacific Ocean.

"There is no doubt this discovery lands a major financial blow right from the South American producers through to the distributors of this product," Coster said.

"This is the single biggest seizures of illegal drugs by authorities in this country by some margin. While this disrupts the syndicate’s operations, we remain vigilant given the lengths we know these groups will go to circumvent coming to law enforcement’s attention."

At a media conference this afternoon, Coster added: "We believe there was enough cocaine to service the Australian market for about one year, and was enough cocaine to service the New Zealand market for 30 years."

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Authorities said no arrests have been made at this stage, but, inquiries will continue into the shipment. They wouldn't elaborate on how they knew where to find the floating shipment of drugs.

New Zealand Customs Service acting comptroller Bill Perry gave an estimate on the intercepted drugs' value.

"The sheer scale of this seizure is estimated to have taken more than half a billion dollars worth of cocaine out of circulation," he said.

"It is a huge illustration of what lengths organised crime will go to with their global drug trafficking operations and shows that we are not exempt from major organised criminal drug smuggling efforts in this part of the world."

New Zealand Defence Force Joint Forces Commander Rear Admiral Jim Gilmour also gave comment on the seizure.

"We had the right people and the right capabilities to provide the support required and it was great to work alongside the New Zealand Police and the New Zealand Customs Service," he said.

"We were very pleased with the result and are happy to be a part of this successful operation and are proud to play our part in protecting New Zealand."