A former New Zealand Navy vessel turned charter yacht has been caught up in an alleged drug plot with $225 million worth of cocaine seized from it in the English Channel.

The Australian Federal Police and UK's National Crime Agency intercepted the charter yacht Kahu on Friday, and seized 2000 kilograms of cocaine allegedly being carried on board, the Herald Sun reported.

The bust of the alleged drug plot and arrest of six suspected criminals - five Nicaraguan nationals and one UK citizen - were the result of the FBI-run encrypted messaging app ANOM.

The Herald understands the Kahu was an ex-Navy vessel that was converted into a luxury yacht for charter by Fitzroy Yachts in New Plymouth.

The police intercept of the Kahu took place when the UK Border Force boarded the Kahu 80 nautical miles off the UK coast.

Built in New Zealand in 1979, the Kahu is now a luxury expedition yacht, with six bedrooms including two VIP staterooms, and an on-deck spa, and an online advertisement listed her sale price as 1.5 million euros, or about NZ$2.5 million.

The yacht departed Barbados on August 3 and was towed to shore at Plymouth where the drugs were seized and forensic examinations took place.

Australian officers based in the UK tipped off the National Crime Agency about an alleged transnational drugs syndicate using Kahu to co-ordinate cocaine shipments. The information came out of Operation Ironside, an undercover sting which involved planting an encrypted app.

Alleged criminals are tricked into using the app, known as ANOM, developed in conjunction with the FBI, and were unaware the 25 million messages sent on it were being secretly monitored.

NCA Deputy Director Matt Horne described the cocaine seized as a "massive haul'' with a street value of 120 million pounds, about NZ$225 million.