A whaling activist who climbed aboard a Japanese whaling ship says he feared the whalers would throw him into the cold Antarctic waters.

"Two guys picked me up by my shoulders and the gunner, the guy who shoots the whales, picked my legs up and they attempted to tip me over,'' Mr Potts said.

"I held on to one of the rails and they knocked my hands off that.''

Sea Shepherd protesters - Australian Benjamin Potts, 28, and Briton Giles Lane, 35 - were transferred to the Steve Irwin ship early today, Melbourne time, after spending three days aboard the Japanese whaling vessel Yushin Maru No. 2, which they clambered aboard on Tuesday.

The Japanese handed the pair over to Australian authorities early this morning on board the customs vessel, the Oceanic Viking.

Speaking publicly for the first time since his release, Mr Potts told 3AW radio he would not face charges over the incident.

When asked if he would repeat his actions again, he replied: "Yes I would''.

"The fact of the matter is they are illegally whaling near a whale sanctuary and illegally whaling in Australian waters,'' he told 3AW.

"I feel that we have the right to inform them of that and inform them on behalf of the Australian people that they're not welcome down here.''

Mr Potts also denied accusations acid was thrown on to the Japanese ship, saying other crew members threw a non-corrosive substance - like "rancid butter'' - to clear the decks and help the pair get on board.

"We weren't given much information at all.  One of our main (aims) was to try and source information out of them,'' he told 3AW.

Earlier today, Sea Shepherd captain Paul Watson said he believed the two men were well.

"We're happy that they were released to the Oceanic Viking and we can pick them up," he told The Age.

"Japan ordered the release but the whalers were trying to get conditions, and we said we absolutely refuse to go along with that."

Mr Potts and Mr Lane will remain with the Steve Irwin as it continues to chase the Japanese whaling fleet, Mr Watson said. He refused to rule out using similar boarding tactics in the future.

"The circumstances that we find ourselves in dictate our strategy and our tactics, so I can't say yes and I can't say no, we'll just have to see.

"The Japanese haven't caught any whales for a week and they (the activists) contributed to that. Now we're going to try for a second week and possibly a third week."

Benjamin Potts' mother, Marianne, told Fairfax Radio she was proud of her "passionate son".

Mrs Potts said she and husband Michael were "very relieved" to know the transfer was successful and their son was safe.

"We have not slept since Monday, we were very concerned for him," she said from her home on Brisbane's bay side.

"We've not had any contact with him at all, although I did ask somebody on board to give him a big hug and a kiss from me, even if he didn't want it, even if it was the captain himself."

Mrs Potts said she was "tremendously proud" of her son's actions.

"We're very proud of his passion and his convictions and I'd just like to say thank-you to the Sea Shepherd group for their support," she said.

"We agree with the Captain's decision not to compromise because it's not just about Ben, it's about a much wider issue."

Mrs Potts also thanked the Australian Government and said all parties, including the Japanese vessel, "acted appropriately".

The whaling fleet, which is on an annual hunt for almost 1000 whales, would now resume operations, whalers' spokesman Glenn Inwood said.

"It became very clear yesterday after 24 hours of receiving no communication from the Sea Shepherd organisation that they had no intention of removing the men from the Japanese vessel and therefore the Australian Government was asked to intervene and take them aboard their Customs vessel,'' he said.

US-based Sea Shepherd, a militant conservationist society, strongly opposes Japan's plan to kill about 1000 whales in the Antarctic Ocean this season.

The group described the activists as hostages and said they were being held illegally as Japan pressed for the group to agree to give up its harassment of the Japanese whaling fleet.

Japan, which says whaling is part of its culture, described the men as unwanted guests and said it was trying to get rid of them safely.

Australia initially dispatched the Oceanic Viking to monitor Japan's whaling as part of a campaign by Western governments to stop the hunt.

Japan uses a loophole in an international moratorium on the practice which allows "lethal research".

with Miki Perkins and AAP