Warning shots were fired by the Army Rangers as they boarded the vessel yesterday during an operation which also involved the Irish Naval Service, Revenue Customs and Gardai.
The ship, which has now been brought to Cork Harbour, is understood to contain a 'significant' consignment of illegal drugs, and could be the largest haul ever seized here.
The operation is thought to be linked to a fishing trawler detained off the coast of Wexford on Monday.
Three men have been arrested.
Tanaiste and Minister for Defence Micheal Martin says the operation is linked to the wider international crackdown on drugs trafficking: