The New Zealand Navy seized about $235 million of high-grade heroin - then let the smugglers free and hosed the drugs into the ocean.
The unusual situation occurred because of limited powers in waters well outside of New Zealand in the western Indian Ocean.
Not wanting to hold on to almost 260kg of heroin, sailors kept small quantities for testing and dumped the rest into the ocean, using a fire hose that ran through a modified green wheelie bin.
The frigate HMNZS Te Kaha has been working in a United States-led operation and seized the huge quantity of drugs after searching two boats.
The drugs were likely to have been destined for Africa and then onwards to Europe and other markets.
It is not known who or what organisations were behind the shipments, but the NZ Defence Force said such drug-trafficking was known to fund terrorist organisations.
NZDF maritime component commander Commodore John Campbell said the haul was a great outcome.
"Under the United Nations Convention of the Law of the Sea, there are articles in there that allow us ... to be able to board vessels on the high seas if we have reasonable reason to think they are involved in illegal activities."
He said disposing of the drugs had been a trial-and-error process.
"We learned this from the Australian Navy - by using just a big green wheelie bin, and then you can spray the fire hose into it ... it means you don't get any blowback on the ship and it's all washed over the side."
Reporters were shown video of Te Kaha's crew boarding a vessel and discovering drugs packed below deck, and later disposing of the drugs.
On June 8 a boarding party from the frigate found 139 one-kilogram bags of heroin hidden on a medium-sized dhow that had been monitored overnight.
Five days later another dhow was boarded after being spotted by a Royal New Zealand Air Force P-3K2 Orion. A seven-hour search found 118kg of heroin.
HMNZS Te Kaha is due back in New Zealand on August 2.