"We just kept going out from one point in a circular search until we found them," said Captain Watson, aboard the Sea Shepherd flagship Farley Mowat. "They were standing up and waving and smiling." Captain Watson said he had thanked the Japanese for their assistance, and then told them, "now it's back to business." He said the other Sea Shepherd vessel, Robert Hunter, was back on the stern of Nisshin Maru.

It is the first time the Japanese whaling fleet has worked in coordination with the anti-whaling ships of Sea Shepherd or Greenpeace. But Hideki Moronuki, whaling section chief of the Japanese Fisheries Agency, told theage.com.au: "Their dangerous activity caused this tragedy. I ask Sea Shepherd and Greenpeace to stop this kind of dangerous activity immediately.'' The inflatable carrying the missing Australian and American was last seen operating alongside the factory ship Nisshin Maru when a sudden fog and drizzle descended on the sea near the Balleny Islands, south west of Tasmania, according to a Sea Shepherd statement.

Sea Shepherd activists had attacked the Nisshin Maru from inflatables after they found it early today, attempting to seal up its drain pipes, and lobbing foul-smelling butylic acid onto its deck. The Sea Shepherd website says seven Australians are aboard the Farley Mowat - carpenter Benjamin Baldwin, deckhand Tom Baldwin, pilot Kylie Burnell-Jones, chief cook Laura Dakin, cook Sara McNabb, 3rd officer Karl Neilsen, nurse Kristy Whitefield.Another Australian, cook Jenifer Gibson, is aboard the Robert Hunter.

The identity of the rescued Australian is yet to be made public. After weeks of searching for the whalers unsuccessfully in the Ross Sea, the two Sea Shepherd vessels appeared to take the fleet by surprise. In their first attack, Captain Watson said his crew cleared the whale-flensing deck of the Nisshin Maru, when they threw a non-toxic "butter acid" on it from an inflatable dinghy.

Activists in inflatables armed with nail guns were also fixing steel plates over drain outlets in the side of the fleeing factory ship, preventing the escape of whale blood from the flensing deck. He said the fleet had scattered and the Robert Hunter was still in contact with Nisshin Maru, which was steaming away at high speed and attempting to use its water cannon on the activists. "They are easily avoided," he said.

The attack came almost five weeks after Sea Shepherd began searching for the fleet in the Ross Sea, and with their vessels beginning to run low on fuel. The group has begun negotiations to enter Australia or New Zealand ports, a decision complicated by their status as "pirate" whalers. The Farley Mowat has been stripped of its Belizean registration, and Britain is to de-register the Robert Hunter in 10 days' time.

Talks are under way with both the Australian and New Zealand Government's in a bid to avoid arrest. Greenpeace's ship Esperanza, which had hoped to be first to reach the whalers, was about a day's sailing away from the position where Sea Shepherd found them, and approaching from the west, a Greenpace spokesman said.

The Japanese Government's Institute for Cetacean Research, which owns the fleet, is harpooning up to 935 minke whales and 10 fin whales under its program of "scientific research". A spokesman for the ICR was unable to comment immediately. - with Jano Gibson and AAP