Three Canadians have appeared in court after almost 100 kilograms of cocaine was seized on a cruise ship docked in Sydney Harbour, the largest amount ever brought into Australia via a passenger vessel.

Officers from the Australian Border Force (ABF), with the help of sniffer dogs, searched the ship's passenger cabins on Sunday and allegedly found 95 kilograms of the drug packed into suitcases.

Tim Fitzgerald, the regional commander for the ABF in NSW, said it was the largest amount of drugs seized at an airport or a cruise ship in Australia.

The ABF worked with the Australian Federal Police (AFP) in investigating the case.

AFP Superintendent Conrad Jensen said the estimated street value of the drugs was almost $31 million.

Andre Tamine, 63, Isabelle Legace, 28, and Melina Roberce, 23, faced charges of importing a commercial quantity of cocaine when they appeared in court today.

They appeared in Sydney's Central Local court via video link from police custody.

The trio did not apply for bail and it was formally refused. They will remain in custody until their next appearance on October 26.

The maximum penalty for drug importation is life imprisonment.

Organised 'international syndicate' responsible for drugs

Mr Fitzgerald said officers were able to undertake a "significant amount of risk assessment on the passengers aboard the vessel prior to its arrival in Sydney and were able to identify high risk passengers".

Police have seized drugs with an estimated street value of almost $31 million from a cruise ship. ( ABC News )

He said officers initially searched one cabin where they found a suitcase containing about 35 kilograms of cocaine in numerous packages and then searched another cabin where they found suitcases containing a further 60 kilograms of the drug.

Mr Fitzgerald said this was not the first time an attempt had been made to import drugs via a cruise vessel.

"We had a similar situation last year … but this is the largest," he said.

"Last financial year alone the Border Force intercepted 18,000 [attempted importations of] narcotics at our various borders, international mail centres, airports, sea ports, sea cargo, air cargo — 22.5 tonnes of narcotics ... have been detected in two years."

He said the alleged offenders were part of an organised group.

"It is an international syndicate … I can't go into specifics about the background of this particular syndicate, but you have to be a very organised … to get your hands on 95 kilograms of cocaine," he said.

"Sydney is highly attractive for cruise ships ... so we're continually risk assessing the cruise ships and the passengers that come by air.

Tim Fitzgerald says the drug seizure today was the largest ever in Australia. ( ABC News )

"This particular cruise ship – because of the nature and the amount of ports it had been to – was considered quite high risk in itself.

"Again the trick is, how do we identify those high risk passengers in amongst the 1,800 people who are just coming here to enjoy Sydney."

He said the vessel stopped at a number of South American ports and the investigation would look into whether the drugs were brought onboard during one of those stops.

The ship in question is the Sea Princess, part of the Princess Cruises fleet which had started its journey in Southampton, England.

"The three Canadians boarded in Southampton, England," he said.

He said he believed the Australian market was the end point for all of the drugs.

'Reality is that this is not the last import of its type'

Superintendent Jensen said the drug seizure was a successful joint operation.

"We believe this is a case of an organised crime syndicate attempting to supply large quantities of cocaine to the Australian community," Superintendent Jensen said.

"The seizure of these drugs has disrupted the supply of cocaine to the streets of Sydney and beyond.

"But the reality is that this is not the last import of its type and of this size.

95kg of cocaine was allegedly found on board the Sea Princess cruise ship. ( Supplied: Princess Cruises )

"We all have a role to play in stemming the flow of drugs, so I would like to stress the message that if people have information, please call Crime Stoppers."

The operation was undertaken in cooperation with the US Department of Homeland Security Investigations, the New Zealand Customs Service and the Canada Border Services Agency.

Earlier, ABF Assistant Commissioner for Strategic Border Command, Clive Murray, said the operation was another example of international cooperation leading to significant results in the fight against international drug syndicates.

The AFP said investigations remained ongoing and they had not ruled out further arrests.

Princess Cruises' owner Carnival said it provided full support to authorities during the police operation.