Two Sea Shepherd ships are struggling northward in the Southern Ocean through another storm, the anti-whaling group says.
The scout ship Brigitte Bardot was struck by a rogue wave that cracked the main hull and severely damaged one of its pontoons on Wednesday.
The Sea Shepherd's flagship, Steve Irwin, went to help and had to abandon the pursuit of the Japanese whaling fleet. It is escorting the Brigitte Bardot to Fremantle for repairs.
"We are watching the Brigitte Bardot very closely," the group's leader, Paul Watson, said on Saturday.
"The seas are getting rougher and the winds are increasing and there is a great deal of pressure being put on the damaged pontoon of the Brigitte Bardot. It looks like we will have to struggle through these conditions for another 24 hours."
The crew of the Brigitte Bardot are wearing their survival suits, Mr Watson said.
The Japanese government security ship Shonan Maru #2 continues to tail the Steve Irwin and the Brigitte Bardot.
The Sea Shepherd ship Bob Barker is still pursuing the Japanese whaling fleet. Last season it shut down the whaling operations on its own.
"This is not going to be a successful year for the whalers," said Bob Barker first officer Peter Hammarstedt of Sweden.
"They have never arrived so late before and they have spent more money for security to protect the whalers from Sea Shepherd than they will ever gain this year from profits from whaling. We continue to pursue them as they continue to run eastward to avoid us. We will not let up on them until they leave the Southern Ocean Whale Sanctuary."
This is the eighth year that Sea Shepherd has pursued the Japanese whalers in the Southern Ocean.
"Our objective from the beginning was to sink the Japanese whaling fleet economically, to bankrupt them. We have succeeded in doing so," Mr Watson said.
"Now the task is to defeat them politically. We are under no illusion that this will be easy. The whalers survive because of massive Japanese government subsidies and much of this subsidy was allocated from the tsunami earthquake defence fund."
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