Ady Gil skipper boards whaling ship

The Ady Gil during its clash with the Japanese whaling vessel Shonan Maru. Photo / Supplied

The Kiwi captain of an anti-whaling boat sunk last month has clambered aboard the Japanese security ship that rammed his boat.

Multimillion-dollar protest boat Ady Gil was hit by the Shonan Maru 2 in the Southern Ocean on January 6, injuring a Kiwi cameraman on board.

The Ady Gil's skipper, Pete Bethune, called the collision "attempted murder" of the boat's six crew members.

This morning, before dawn, Mr Bethune raced to the Shonan Maru 2 on a jet ski to get revenge.

He leapt on to the Shonan Maru 2's railings carrying citizens arrest papers for the Japanese captain and a $3 million bill for his lost boat.

Mr Bethune waited more than an hour on the Japanese ship's deck until sunrise, while a helicopter from his protest group, Sea Shepherd Conservation Society, hovered overhead to film the ensuing exchange.

When Mr Bethune knocked on the bridge door, a Japanese crew member came out, tried to shoo him away, and walked back inside, ignoring the Kiwi intruder.

So Mr Bethune opened the door himself and walked into the Shonan Maru 2's bridge.

Paul Watson, skipper of the boat that took Mr Bethune to the Shonan Maru 2, said he expected that Mr Bethune had been detained.

He had made radio contact with the Japanese, who confirmed Mr Bethune was on-board, Mr Watson said.

Mr Bethune had taken action because of the double standards protecting Japanese whaling ships from prosecution.

The Sea Shepherd Conservation Society had filed a complaint of attempted murder with New Zealand police but nothing came of it.

"[Mr Bethune] wants New Zealand to press charges. He's quite angry that the New Zealand Government has done nothing to represent him and his boat," Mr Watson said.

The Japanese whaling fleet should be embarrassed Mr Bethune had managed to breach their security so easily, he said.

Foreign Minister Murray McCully would not comment at this time.