Found in a bale with a buoyancy aid and beacon attached, at least 300kg of cocaine were seized on a bulk carrier ship, which had docked in Foynes.
It is believed that the bale were the drugs were found was intended to have been thrown overboard, and collected by a "daughtership".
The drugs were seized by Customs officers, with the cargo ship being detained pending a full search, to see if there are any more drugs found on board. This search could take several days.
The vessel's crew will also be detained in Ireland, where they will be questioned as part of this investigation.
Along with local gardaí, national units were also involved in the operation, including the Drugs and Organised Crime Bureau.
At the time of writing, no arrests were made.
This also marks the second such drug seizure from a bulk carrier, following September's seizure of over 2,000kg in drugs, which were valued at €157m from a MV Mathew off the south coast.
