Anti-whaling protestors used rancid butter in their latest attack on Japan's whaling fleet in the Antarctic.
Japan said some of its crew were hurt as bottles of an acid made from the old butter were thrown onto the ship by the Sea Shepherd campaign group.
But the group denies that any of their missiles actually reached the ship.
Japan's whaling fleet has been catching whales for what they say is scientific research, but lots of environmental groups think the hunt is wrong.
Campaigners and whalers have clashed several times since the hunt began in November, with some groups, like the Sea Shepherd, following the ships to try to stop them.
Australian fisheries officials said more than 100 of the glass bottles were thrown at the Nisshin Maru.
The whalers responded by hosing down the activists during the hour-long attack, which lasted until protesters ran out of ammunition.
A Japanese spokesman said: "This is an act that tries to unfairly harm the safety of a ship and crew that is acting within the law at sea. It's an unforgivable act and we protest strongly."
Last year, Japan faced international criticism over its plans to kill endangered humpback whales in the Antarctic as part of its annual whale hunt.
It later abandoned plans to kill humpbacks but said it would still kill about 1,000 other smaller whales for scientific purposes.