The investigation, dubbed "Operation Beech", has led to the arrest of 12 people with alleged links to the Mexican drug cartel.
WA Police Commissioner Col Blanch said the operation spanned six weeks and involved intensive surveillance and resources.
"This was an opportunity to catch the syndicate - the group of people that were capable of receiving it, landing it and then distributing it across Australia," Commissioner Blanch said.
"The message from the WA Police Force is unchanged … we will come after you, regardless of where you live on this earth."
In an even bigger operation last month, New Zealand authorities intercepted more than three tonnes - 3894 kg - of cocaine floating in the Pacific Ocean - the largest find by "some margin".
Police Commissioner Andrew Coster said then given the large size of that shipment it would have likely been destined for the Australian market.
The US Drug Enforcement Administration intercepted 2.4 tonnes of cocaine bound for WA off the South American Coast in November.
Intelligence suggested the alleged drug traffickers were unaware of the seizure and the Australian arm of the syndicate was expecting to receive the shipment around December 28.
WA Police substituted the cargo for fake cocaine using identical packaging and dropped it 40 nautical miles west of Perth while keeping an eye on it using drones and helicopters.
It is alleged that the syndicate used two boats, Catalina and Cool Runnings, to make several attempts to find and retrieve the cargo.
On 30 December, Tactical Response Group officers arrested three men onboard the Cool Runnings with approximately 1.2 tonnes of the fake cocaine, after the boat had washed up on the beach near Moore River, 70km north of Perth.
It is alleged that others, onboard the Catalina, went looking for Cool Runnings, towing it back out to sea to transfer the fake drugs, before Cool Runnings sank.
Raids were carried out across Perth, including on the Catalina at Hillarys Boat Harbour, as well as various hotels.
Police also stopped a vehicle on the Great Eastern Highway, near Coolgardie, where they found more than A$2 million in cash.
They charged a 39-year-old man and a 37-year-old woman allegedly connected to the syndicate.
The 12 people who have been arrested are from WA, New South Wales, the Northern Territory and United States.
Operation Beech was a joint effort between WA Police Force Transnational Serious and Organised Crime Squad and the Sydney Office of the Drug Enforcement Administration, with assistance from other state policing jurisdictions.
WA Deputy Commissioner Tony Longhorn said implementing collaborative and innovative strategies in police intelligence would be key to tackling future drug activity.
"It's a confidence booster … every time we do these operations we're testing the limitations of our capabilities," the Deputy Commissioner said.
"The criminal syndicates are changing up the game all the time, and we have to change up ours."
Police confiscated 2.4 tonnes of cocaine in a western Australian operation. Photo: Screenshot / Western Australia Police Facebook