The arrested men, aboard the Kahu, a luxury Jamaican-flagged yacht sailing from the Caribbean, included a suspect from Stockton on Tees and five Nicaraguans.
They reportedly had no idea they were being monitored in an international operation on Thursday evening led by the British National Crime Agency (NCA) and Border Force and supported by the Australian Federal Police (AFP).
Border Force Maritime Command’s 42-metre cutter ‘Searcher’ and 19-metre coastal patrol vessel Alert had covertly identified and monitored the Kahu’s movements.
An NCA spokesman said: “In international waters north of Guernsey, specialist highly-skilled Border Force and NCA officers carried out the complex interdiction and boarding of the Kahu.
“It was escorted back to the UK mainland where a team carried out a deep rummage search and discovered the enormous haul of Class A drugs.
“The arrests demonstrate the strength of the NCA’s international partnerships — working with the AFP who as part of the operation used evidence from their Operation Ironside — the country’s investigation into the ANOM encrypted comms platform.”
The ANOM system was set up by the FBI in the US and covertly distributed to top-level criminals who were then monitored by police globally.
The sting ran from 2018 and in June this year, a series of raids and arrests were carried out across the globe.
The men, whose ages range from 24 to 49, were arrested on suspicion of drug trafficking and are in custody awaiting interview.
Matt Horne, NCA deputy director, said: “This is a massive haul of cocaine with an estimated street value of around £160m.
“There’s no doubt these drugs would have been sold on into communities across the UK in such ways as county lines fuelling more crime and misery.
“Organised crime groups are motivated by money. The deprivation of these drugs will smash a hole in the OCG’s plans and ability to operate.
“Also, the arrests of the men transporting the drugs means the crime group has lost trusted offenders who would have been key to their operation.
“We continue to work with partners at home such as Border Force and those abroad such as the AFP to protect the public from the class A drugs threat.”
AFP Assistant Commissioner Lesa Gale, said: “Intelligence from Operation Ironside had enabled the AFP to assist international enforcement partners in disrupting an alleged sophisticated criminal network.
“Operation Ironside has opened the door to unprecedented collaboration across law enforcement agencies around the globe.
“This result highlights the importance of the AFP’s partnership with the NCA to combat offshore transnational organised crime that impacts both of our countries.
“The AFP and NCA have a strong, historic relationship and both agencies recognise the significant threat to national security posed by transnational organised crime.”