A Sussex activist held captive for two days on a Japanese whaling ship said today he feared he would be thrown into the sea after boarding the vessel.

Giles Lane said he knew there was a risk he would be detained before he boarded the harpoon boat Yushin Maru 2 on Tuesday, but said he had no regrets about what he had done.

The 35-year-old pledged to continue efforts to disrupt the Japanese whaling fleet's activities in the Southern Ocean.

Mr Lane, from Fulking, near Brighton, boarded the ship with a colleague from the anti-whaling Sea Shepherd Conservation Society.

"The crew's initial reaction was to try to throw us back overboard into the ocean," he said.

"There were some worrying moments, but it happened too quickly to be scared.

"Then there was a slight scuffle and they tied us to the railings and left us to get a soaking in the icy water."

Speaking from the Sea Shepherd vessel Steve Irwin in the Southern Ocean, Mr Lane added: "We couldn't have been washed overboard, because we were chained to the railings, but when the captain turned the ship sharply we were thigh-deep in water. We could have got hypothermia."

Mr Lane and his Australian colleague Benjamin Potts were then locked in a cabin in the ship for two days before being transferred to Australian customs ship Oceanic Viking after an impasse between the Japanese fleet and the activists' vessel was resolved with an agreement brokered by the Australian government.

The pair were then shuttled back to the Steve Irwin, officials said.

Mr Lane said he and Mr Potts had boarded the Japanese ship so they could hand the captain a letter telling him he was breaching international law by hunting the endangered mammal.

"We're still out here disrupting the Japanese whaling fleet, and we'll continue to do that as long as our fuel and food lasts," he said.

"Although we appreciate the concern that people have expressed for our welfare, it is important to remember that this is not about us.

"It's about stopping this cruel and illegal whale hunt. The treatment that we received was trivial in comparison to the suffering that the whales experience at the hands of the Japanese whalers.

"I imagine if you could ask the whales, they would think it was a worthwhile thing to do."

Paul Watson, captain of the Steve Irwin, said the ship would continue its pursuit of the seven-strong Japanese fleet.

He said: "Every day that we stop the whalers is a victory. We will continue to intervene, harass, block and obstruct the whalers at every opportunity."

Last night Mr Lane's girlfriend, Jen Parker, originally from Windermere, Cumbria, said she was "delighted" at the news he was safe.

Ms Parker, also 35, said she believed Mr Lane - her partner of 10 years - would want to stay on in the Antarctic to continue the anti-whaling campaign.

She said: "I'm sure Giles will want to carry on his campaign to stop whaling in the Antarctic. That's what he went out there to do, and I can't see him stopping now.

"I'm certainly not expecting to see him for a while yet, but to know he is safe and well will be great."

Australian foreign minister Stephen Smith said police were investigating complaints in connection to the incident to determine if any laws had been broken.