Around £60 million worth of cocaine heading to the UK has been seized in one of the largest drug busts in recent years.
Officials from the National Crime Agency had been carrying out a “long-term” investigation into an organised crime ring importing class A drugs into the country from South America when they made the discovery.
Officers from the UK Border Force cutter HMC Protect boarded a sailing yacht off the coast of Wales on Tuesday morning.
Packages of cocaine weighing more than 250kg had been recovered by midday on Wednesday and searches on the vessel continue.
Investigators believe that there is an additional 500kg still stashed on board.
Two men, aged 41 and 53, were arrested on the yacht.
Four others - three men aged 23, 31 and 47 and a 30-year-old woman, were arrested in Liverpool and Loughbrough.
They have all been released on bail until late September.
Craig Naylor, deputy director of investigations for the NCA, said he believed the drugs bust was their second biggest in recent history.
He said: "We believe at the moment what we've taken off the boat has a wholesale value of £8 million, and the street value of that will be in excess of £20 million.
"That's likely to rise as we take more product off the boat, so as an estimate the wholesale value would be £20 million in total, and a street value of £60 million.
"This is a very high end job - 750kg (1,654lb) of cocaine. You don't come across that every day of the week.
"The NCA, working with border force, working with other partners, are regularly seizing, arresting and convicting people for these sort of offences, but usually for 10kg-20kg (22lb-44lb) amounts.
"Certainly in my recollection this is the second biggest seizure that the NCA has had in recent years."
Mr Naylor said the UK had seen a rise in violence and drug-related crimes including county lines trafficking in the last "three to four years" and Tuesday's seizure was part of a "frontline defence" by the NCA to tackle the supply of drugs into the country which fuels the criminality.
Steve Whitton, deputy director of the Border Force's Maritime Command, said: "This is a major seizure and a testament to the multi-agency approach we take to secure the UK's border and territorial waters.
"Our collaboration with the NCA, combined with excellent work from the crew of HMC Protector and officers from our specialist deep rummage team, ensured that the sailing yacht Atrevido's cargo did not reach its intended destination.
"Working together, we will continue to do all we can to put the organised crime groups involved in drug smuggling before the courts."
