When armed Russian coast guards descended on to the Arctic Sunrise from helicopters and screamed at everyone to get on the ground, Captain Peter Willcox took it as just another day at work.

The 60-year-old American has a long history of entanglements with law enforcement across the world, and has been arrested at various times in Turkey, the Philippines, Peru and Denmark. He was also the captain of the Greenpeace ship the Rainbow Warrior, which was bombed by French special forces in 1985, not long after the start of his 32-year affiliation with the environmental organisation.

"It didn't seem to be that unusual," said Willcox, during an interview at the hotel in Saint Petersburg where the Greenpeace Arctic 30 are staying since their release on bail in recent days, an empty bottle of Merlot on the table and a selection of English-language magazines strewn across the bed.

"When guys come on board with machine guns, they're going to take control and you're going to sit down. That's understood. The shock was when we got back to Murmansk and they said the word piracy."

Despite being arrested across the world, Willcox had never spent more than a night in a cell until the ill-fated Arctic voyage. "In Turkey, we had a trial and at one point my lawyer looked at me and said you're going to get three months, but 15 minutes later we were walking free," he recalled.

"I did spend a night in a Danish prison but it was nicer than many of the hotels I stayed in that summer."

Spending two months in Russian prisons, first in the Arctic port of Murmansk and then in Saint Petersburg, was a very different experience.

"The first five weeks when we were being hit with the piracy charge I lost a lot of sleep," he recalled. "I was nervous, I was scared. I just couldn't believe that they were going to put us to jail for years and years. You keep telling yourself you know they're not going to do it, but then a month later you're still sitting there. If I'm in jail for five years, I never see my father again, maybe my mother too. That's a game changer."

Russian authorities initially accused the 28 Greenpeace activists and two freelance journalists with piracy for their protest against oil drilling at the Gazprom-operated Prirazlomnaya rig, in the Pechora Sea. This was later downgraded to hooliganism, which still carries a maximum jail term of seven years. The first sign of a relaxation in policy from Russian authorities came last week, when courts in Saint Petersburg began to free the activists on bail. Only two remain in jail, Briton Philip Ball and Australian Colin Russell, but both are expected to be freed soon.

Willcox, who was released on Friday, started out as a youngster on the fringes of the civil rights movement in the US, and having experienced the "tremendous feeling of optimism that we can get the job done", thought things would be similar when he began working on environmental issues 40 years ago, and that in five or 10 years, laws would be passed that improved the situation.

Willcox with the Rainbow Warrior, which he also captained, in Sydney harbour, in 1986. Photograph: Patrick Riviere/Getty Images

"But every year it gets worse, and now it's got to the point where I'm honestly scared for the future of my kids. I don't feel like I can stop."

After the Rainbow Warrior incident, in which photographer Fernando Pereira died, Willcox said his determination to fight for the cause only increased. Although he suffered greatly over the death of Pereira, he said the French response was a "reaffirmation" of the importance of the cause. "If we had got them so scared, a boat full of hippies with a single old sideband radio, we felt we must have been doing something right."

Nevertheless, nearly three decades later, he is more cautious. British detainee Anthony Perrett told the Guardian that if he could turn back the clock, he would still travel on the protest but Willcox says the experience will change his perspective, even if he does plan to be back captaining the new Rainbow Warrior in February.

"I'm going to be much more conservative with the way I do actions in the future," he says. "You can't go through what I went through and not have it affect you."

As for the ship itself, the Arctic Sunrise is moored in Murmansk harbour under the guard of Russian authorities. "I really liked that boat. I'm feeling bad for it, and I'm hoping we can get a crew on as soon as possible and get her out of there."

During his incarceration in Murmansk, he was taken by Russian investigators as a witness on to the ship several days running, where he stood, in handcuffs, and watched as they tore through the boat. "They went through everything, took every hard drive out of every machine they could find. That's the heart of the boat. I watched them go through people's cabins. They took our cash, wallets, laptops, phones, and I don't know if we'll ever see that again."

Although the 30 still face hooliganism charges, the rumour in Saint Petersburg is that they could soon be allowed to leave Russia. It is unclear whether Russia would fully drop the charges against the activists or simply turn a blind eye to them leaving.

A Greenpeace spokesperson refused to comment on the rumours, and said "it will only be over when they all land at airports in their home countries around the world".