The Policía Nacional said it was the first time it had come across unmanned underwater vehicles being used for drug-running.
The eight were arrested in Cádiz, Málaga and Barcelona after officers seized 145kg of hashish, 8kg of marijuana, €157,370 in cash, and six large aerial drones that could cover a distance of 30km.
Six of the eight people charged with drug trafficking and belonging to a criminal organisation have been remanded in custody.
“Three unmanned underwater vehicles were recovered, one of them almost finished and two still under construction,” the force said in a statement. “They were due to be delivered to French narco-traffickers to be used to transport significant quantities of cocaine.”
The gang had specialised in building false boat bottoms and hidden storage compartments for cars and trailers which they supplied to smugglers and other criminal gangs.
However, they also had a side line in marine drones, police said.
“They were making large, unmanned drones with huge load capacities that meant they could carry a cargo of between 150kg and 200kg,” the force said. “Among other uses, this equipment would have allowed drug traffickers to transport large quantities of drugs across the strait of Gibraltar by remote control.”
The 14-month investigation was carried out in partnership with French police.
It was discovered that the gang had been supplying logistical help to clients in Italy, France and Denmark, as well as to criminal gangs in Catalonia, the Costa del Sol, the Campo de Gibraltar, and Ceuta, one of Spain’s two north African enclaves.
In February, five Spaniards and two Ecuadorians were jailed for their parts in a plot to ferry 3,068kg of cocaine, worth an estimated €123m across the Atlantic from Brazil to Spain in a homemade, semi-submersible “narco-submarine”.