The haul, weighing 581kg (1,280lbs), was found aboard a dhow that was intercepted by the HMAS Newcastle off the coast of east Africa.
The Australian vessel is part of the Combined Maritime Forces (CMF), an international patrol mission.
The CMF aims to tackle piracy, terrorism and drug smuggling.
The naval partnership, involving 30 countries, patrols 2.5 million square miles of international waters in the Indian Ocean and around the Middle East.
