Customs officers recovered 22 bales of cannabis resin worth £2.5m yesterday.
The haul, which weighed a total of 650 kilograms, was fished out of the sea off the east side of the Rock.
Officers from HM Customs (Gibraltar) spotted the bales while patrolling through British Gibraltar territorial waters.
“It is believed that these must have been jettisoned by smugglers but no arrests have been made,” a Customs spokesman said.
Customs and the Royal Gibraltar Police have reported increased smuggling activity at sea in recent months, as have law enforcement agencies in Spain.
Often when chased, smugglers ditch their shipments in order to increase the speed and manoeuvrability of their vessels during high-speed pursuits.
The bales were in good condition and it is not believed that they were in sea for long.
“There’s a lot of traffic out there and these drugs were fresh,” the Customs spokesman said.
“They hadn’t been floating around for long.”
This is the latest in a string of similar drug hauls in British waters.
Yesterday evening, Customs and RGP units were still combing the shoreline and had not ruled out recovering more bales of drugs.