Activists will use a ship bought from the Japanese government by stealth to defend whales and disrupt krill fishing in Antarctic waters.
The 64-metre vessel, previously named Arasaki and now The Bandero, has docked in Hobart after being purchased by the Captain Paul Watson Foundation.
The organisation, set up by Sea Shepherd founder Paul Watson, uses "aggressive non-violence" to protect whales and other marine life.
The foundation believes Japan is eyeing a return to whaling in the Southern Ocean after building a long-distance "mothership".
The foundation says it plans to use The Bandero to target krill fishing operations in Antarctica.
"Our intention with this new vessel is to be a protector and defender of Australia's marine life in Antarctica," captain Locky MacClean said on Friday.
Mr MacClean said the ship had a better range than previous foundation vessels and would be able to stay in Antarctica for an entire season.
The Southern Ocean is a designated whale sanctuary, meaning all commercial whaling is banned.
The Japanese embassy, which has been contacted for comment, told The Australian newspaper the country had no plans to take whales from the Southern Ocean.
Foundation CEO Omar Todd said the foundation created a buffer of companies to buy the ship, claiming it would be used to conduct ocean surveys.
"In Japan, (the vessel was) run by the government, by the fishing department," he said.
"We knew if they knew we were looking at purchasing it ... it would be an absolute no-go.
"There is enormous and intense interest in the vessels we purchase."
Mr Todd said the aim was to berth The Bandero, named after the Tequila brand of American billionaire and foundation supporter John Paul DeJoria, in Hobart.
But he said higher than expected berthing fees may force it to find a home on mainland Australia.
Former Greens leader Bob Brown has urged the Tasmanian government to ensure the boat pays a lower berthing fee as a non-profit vessel.
The foundation plans to use another vessel, a former Scottish fisheries patrol ship, alongside The Bandero at the end of the year in its Southern Ocean campaign.
