FOUR members of the Byron Whale Action Group were among 30 protesters who tried to hand a letter to the German Consulate in Brisbane on Friday demanding the release of Sea Shepherd marine conservation founder Paul Watson.
Capt Watson, a Canadian, was arrested in Germany last week on what Sea Shepherd says is a trumped-up charge of attempted murder.
He may be deported to Costa Rica, where the organisation says he would not get a fair trial because the government there benefits from the shark fin trade.
The charge relates to an incident at sea where Capt Watson's vessel nudged a shark-finning trawler.
Sea Shepherd urged its supporters to act "not only to save the life of Captain Watson, but also to save the lives of the whales, dolphins, seals and fish that he has spent his life courageously defending".
Madison Stewart from the Byron group said two of the protesters had attempted to deliver the letter but were denied access to the building lifts by security officers.
"We tried to get our message across with banners and posters," she said.
Dean Jefferys from the Byron Whale Action Group said he had written to Richmond MP Justine Elliot urging her to ask Foreign Minister Bob Carr to speak to the German Foreign Minister.
"It (the arrest) is inspired by governments like Japan and corrupt people who profit from illegally killing whales, sharks and other marine wildlife," Mr Jefferys said.
"If he is extradited, the Taiwanese shark-finning mafia reaches not just to the illegal fishing industry in Costa Rica, but also to the prison system there. He would likely not survive jail long enough to see the inside of a court room."
Sea Shepherd Queensland co-ordinator Mark Clough said the protest on Friday had been part of action by crew, staff and supporters in other Australian cities, and also throughout the world.