A Devon-based warship has been involved in the seizure of 12.4 tonnes of cannabis resin which was being smuggled in a small cargo boat.
Crew from the Type-22 frigate HMS Cumberland, based in Devonport, Plymouth, covertly tracked the dhow in the Gulf of Aden before boarding it.
A search team found the resin in large bales in a hidden compartment.
The Royal Navy said the resin, which it destroyed, was sufficient to make about 35 million cannabis cigarettes.
The navy team originally boarded the vessel to conduct a check of its official documentation.
However team members became suspicious and conducted a more extensive search of the boat, finding the compartment containing the bales, the navy said.
It was later identified as cannabis resin and destroyed.
Petty Officer Jan Dash, who was part of the boarding team, said: "You don't expect to find this quantity.
"Twelve tonnes is a huge amount of drugs and looked like bags of potatoes piled up when we got it on deck."
HMS Cumberland's captain, David Dutton, said the operation was a "significant success" for the frigate and coalition forces in the area which were part of Combined Task Force 150.
He said: "The clear message is that the Royal Navy is here, ready and able to stop the proceeds of smuggling reaching terrorists and insurgents."
The navy said it verified with the Serious Organised Crime Agency (Soca) that the amount of drugs seized could have made 35 million cannabis cigarettes.
HMS Cumberland set off from Plymouth on her deployment on 25 May. She is due to return to her home port at the end of the year.