Visiting the Galapagos Islands has been a lifelong dream for BBC presenter Liz Bonnin. She talks to Sarah Marshall about her ambitious new series

Even a worldly wildlife TV presenter can never underestimate the power of nature. Celebrity biologist Liz Bonnin was reminded of that fact while filming new three-part BBC One documentary Mission Galapagos.

"I've had a few wildlife experiences where you get a sobering reminder of the power of the planet," she says, recalling a stomach-flipping dive below the waves in a Triton submersible, when strong currents threw her expert team off kilter. "It's great, and quite a healthy thing to happen to you.

"At one point pilot Buck Taylor went very quiet and I knew we were in trouble," she adds, shuddering as she describes the nail-biting episode. "There was this massive wall of soupy, opaque dark green water heading straight for us, and we were trying not to crash into the other submersible. The two of us were just spinning around in these currents like we were in a washing machine."

Plunging into murky ocean depths, that have never before been studied by science, was just one of the daring research missions Bonnin embarked upon for the ambitious new series, which she hopes will help audiences better understand the serious challenges facing animals in this remote archipelago, 600-miles off the coast of Ecuador.

"We know about the Galapagos as the beautiful, wonderful haven; a place where we've got things right," explains Bonnin, who refuses to disclose her age but is somehow 44, according to the Internet. "And as much as it still is - and it is much more pristine than many of the wild places left on our planet - it's not immune to the effects of our human footprint. The more we understand that every ecosystem is intrinsically interlinked to the next, we understand that everything we do here in the UK affects the Galapagos."

Bonnin spent an intense three weeks on board research vessel Alucia, shadowing scientists carrying out groundbreaking research. She scaled Wolf Volcano searching for near extinct pink iguanas; dipped 1,000m below the surface to collect samples of unknown corals and anemones; and scuba dived amid 600-strong groups of scalloped hammerhead sharks partaking in a "complex mating ritual", the world's largest gathering of the endangered species.

"Darwin's Arch is probably the most revered dive site in the world," says the presenter. "Hanging on for dear life to the reef before the currents sweep you away into the Pacific is quite an experience. The hammerheads appear overhead and you forget everything except to breathe slowly and enjoy this once in a lifetime sight."

Bonnin, who is now in Australia for BBC Two's Stargazing Live, claims her submersible dives were "the closest I'll ever be to what it feels like to be an astronaut - to be exploring this mysterious, other-worldly place".

Following her first dip in the multi-million pound piece of kit, also used by Sir David Attenborough in his Great Barrier Reef series, she enthuses to camera that the experience "trumps" anything she's done before. So is it fair to say French-born, Irish Bonnin enjoyed some of her best wildlife moments ever during filming for the series?

"Oh yeah! It really was extraordinary. It won't be easy to match. It was my first visit. Charles Darwin is one of my absolute heroes and it's been a dream of mine to go there for so long," adds the presenter, who studied biochemistry and wild animal biology. "I had an idea of this mystical place, where all these impossible animals are living beside each other, and I was interested to just meet them."

Even now, typically calm and composed, Bonnin shivers with excitement while recounting memories from her trip. She claims to have fallen in love with "every single species because they are so incredibly unique", although a couple of creatures have earned a special place in her heart.

While performing underwater somersaults with boisterous Galapagos sea lions, she delights in a humorous encounter with one of the archipelago's most "comedic" characters.

"This flightless cormorant swam right up to me and started pecking my mask and I couldn't help but giggle," she tells me, laughing.

But the star of the show is undoubtedly the marine iguana, a black, scaly mini-monster who charmed audiences of Planet Earth II during a death-defying escape from writhing racer snakes.

Described by Darwin as "imps of darkness", Bonnin agrees the islands' endemic reptiles aren't the most attractive specimens. "I was doing a piece to camera and there was this really big, ugly male behind me. He looked like the bad guy in the group, the bully, and he was giving everyone else hell. He kept snorting sea water to get rid of the salt they ingest, and it was hitting the back of my neck. It was so unpleasant."

But she praises their remarkable survival skills.

On Fernandina, the youngest island in the Galapagos, the team discovers how the animals shrink their bones during bad El Nino years, enabling them to exist on reduced food supplies, and then expand again once conditions improve. "It's mind-blowing stuff," marvels Bonnin. "They're like marine iguana accordions".

As well as serving up plenty of entertaining TV moments, there's a sense Mission Galapagos is actually contributing to science through ground-breaking findings and helping to facilitate vital research work. It's a direction Bonnin hopes to take with her future nature programmes.

"It's our duty to help communicate what we believe is the most important thing - to understand the wonders of this planet and do everything in our power to protect it.

"Now it's about collaborating on a whole new scale. It's about playing a real hand in using the resources we have available to help science move on and make great advances. I love that notion. It's what my academia was all about; to be able to combine that with communication is the perfect marriage. It's in my DNA."

Yet, despite her newfound love for the islands and her appointment as an ambassador for the Galapagos Conservation Trust, Bonnin is uncertain she'll return. "Don't get me wrong, I'm desperate to go back," she says, "but if I'm really responsible, I'm going to step back and let someone else have their once in a lifetime trip."

  • Mission Galapagos begins on BBC One on Thursday, March 30