As British actor Martin Clunes takes in 16 of Australia's 8220 islands for a new three-part documentary series, he is perhaps not the most steely of adventurers.

Wading into shallow waters on Ned's Beach on Lord Howe Island, he shudders as the harmless fish swarm around him. "Look at the size of that one. God almighty," he exclaims.

Elsewhere, on a simple fishing trip off Restoration Island in far north Queensland, he shrieks and quickly retreats as a golden trevally flaps about as it's brought on board.

"That's a grisly business," he remarks on the boat as the fish is put out of its misery. "I'm a bit of a wuss about all that."

Talking on the phone from the comforts of his Dorset farm and revisiting his journey around Australia earlier this year, he's defensive about his outdoor skills.

"What are you saying?" he says, laughing. "So long as I'm not confronted with any flappy fish, I'll be fine."

Clunes is best known as the curmudgeonly, misanthropic GP in the long-running drama Doc Martin, which, he says, despite reports to the contrary, is to continue beyond next year. The real Clunes is a warm and engaging host on Islands of Australia as he visits some of the nation's lesser-known spots, meets the locals and delves into the culture and history of these remote enclaves off the mainland.

The show was inspired by another documentary he made – Islands of Britain, in 2009 –after which Seven approached him to make a version Down Under. He says it took a lengthy time to get made because of the logistics.

"I'm a bit of a baby about going away from home," he says. "I tend not to like to be away for more than two weeks. So it was like being on an oil rig: two weeks on, two weeks off, for three visits."

The show itself attempts to unpick the diversity and challenges of island life, beginning in Sydney's Fort Denison and spreading to examine the convict heritage of Norfolk Island, the cultural crossroads of Thursday Island, the indigenous culture of the Tiwi Islands and the penguins of Phillip Island, among other destinations.

A highlight, he says, was coming across one of the inhabitants of Ningaloo Reef.

"Oh my god, just extraordinary," he says. "I just sort of flippered alongside this beautiful eight-metre female whale shark and became completely hypnotised. I guess we went along for half an hour, 40 minutes. I don't know how much water we covered in distance, but just gazing at her, her body, how it works, the musculature working, comparing it to other large animals that I know, but [it was] a real take-your-breath-away [moment] and just the fact that she was so unbothered by our presence."

It's not just the wildlife that is fascinating. A notable character is Dave Glasheen, a "real-life Robinson Crusoe". A former Sydney businessman, he lost everything in the 1987 sharemarket crash and now, at age 72, has been the only inhabitant of Restoration Island for nearly 20 years.

This tricorne-wearing, bearded, shirtless eccentric was Clunes' host for a couple of nights with some interesting sleeping arrangements in the humid, mosquito-heavy Queensland climate.

"He doesn't run a hotel there," says Clunes, deliberately playing down the state of affairs. "It was a bit of take-your-pick, there was a hut here and a hut there, and there was a washed up yacht on the beach and I thought, ooh, that looks romantic, I'll take the yacht, but it was so hot I couldn't sleep in it. I had to sleep on top of it, but so then I was exposed so I had a shirt buttoned up to my chin, and trousers tucked into my socks so the mozzies couldn't get me."

Clunes is no stranger to a documentary – he came out to Australia in 1999 with his Men Behaving Badly co-star Neil Morrissey for the series Men Down Under, following the path of the Olympic torch and investigating the Aussie male. A keen animal lover – flappy fish aside – he's also tackled programs about man's working relationship with horses, dogs and endangered species.

"I love it, I love it, " he says about making documentaries. "Because I don't have to learn any lines. It's very free, it's very easy for me. I'm very comfortable around cameras so that's not a worry for me.

"I'm not a professional presenter, in that I could present a programme about something I wasn't interested in, so I only do things I'm genuinely interested in. So I genuinely go on and satisfy my curiosity, and the fact that there's a camera there, so much the better."

WHAT

Islands of Australia

WHEN

Seven, Friday, October 7, 8.30pm.