Robert Irwin Is All Grown Up and Baring Almost All for Shocking Underwear Ads — See the NSFW Pics! (Exclusive)

• Robert Irwin, the son of late Crocodile Hunter Steve Irwin, dares to bare in a jaw-dropping new underwear campaign for Australian brand Bonds.
• The conservationist, 21, models with venomous snakes and spiders for the provocative ads.
• “I’ve done more sit-ups and had less carbs than I ever have in my life,” Irwin tells PEOPLE of prepping for the shoot in an exclusive interview.

Robert Irwin is giving a peek at what’s down under.

The son of late Crocodile Hunter Steve Irwin leaves very little to the imagination in racy new ads for Bonds, the Australian underwear brand that’s launching in the U.S., and he tells PEOPLE that he had no hesitation about his nearly naked modeling moment.

“It was a pretty immediate yes,” the 21-year-old conservationist and TV personality says with a laugh.

“I wish I could say I was very suave and cool about the whole thing, but I was like, ‘Yes! Let’s do it!’ Because Bonds in Australia is an absolute icon,” he adds. “Also, I’m at this point in my life where I’m trying to do as many different and random exciting things, and if it’s something that makes me a little bit nervous, that I’ve never done before and it’s a bit of an adrenaline rush? That’s what I want to be doing.”

The former zookeeper says he also had no qualms about posing with snakes, lizards, and spiders (most of which were venomous!) for the “Made for Down Under” campaign.

“I mean, I’ve spent my life wrangling crocs and snakes and rescuing animals. And so to feature a little slice of that excitement in this new campaign, mate, it has been so much fun. I mean, I’m surrounded by spiders and snakes except [this time] I’m in my undies. That’s the only difference.”

So which is scarier: wrestling a croc or stripping down to your skivvies for a photoshoot?

“Getting your gear off is way scarier than wrangling a croc!” he says.

“Wrangling animals is easy… and I had to do both. It was not on my bingo card. It felt so surreal. But it’s true what they say about Bonds, mate. They keep you comfy the whole way through.”

As for how he got into shape for the shoot, he says health and wellness are a part of his everyday life.

“I’ve got to stay pretty fit with all the crazy stuff I’m doing,” he says. ‘I’m saving crocodiles, I’m in and out of the Aussie bush every day and it’s hard work, so you’ve got to keep pretty good upper body strength, good stamina.”

Still, he admits he snuck in some extra workouts — and avoided the Vegemite on toast!

“I’m representing Australia!” he says. “So I wanted to look my best and to feel my best and just feel really confident. And so I’ve done more sit-ups and had less carbs than I ever have in my life, but it’s been fun.”

He adds, “At Australia Zoo, our beautiful wildlife sanctuary, it’s great, I’ve got about 700 acres to just run. So I’ve been doing a lot of sprints, a lot of hill sprints.”

Plus, he was able to get tips from his most inner circle.

“My brother-in-law Chandler, he’s a professional athlete so he gave me a lot of great tips. And my mom actually did bodybuilding! She had more biceps then than I’ll ever have!”

He says his family, including his sister Bindi, fully supported him doing the racy shoot.

“My family are so supportive, I just love them so much. They’re the solid foundation to everything I do, and what we’re doing together.”

Irwin says as long as his cheeky ads bring awareness to animal conservation, he says it will have been worth it.

“We are all trying to continue an important legacy that my dad started,” he says. “I’ve gotten to find my own individual ways of doing that, and sometimes that comes in the form of modeling Bonds! It seems so out of the ordinary for what I would do, but I get to be with Aussie Wildlife, I get to approach a new audience, a new platform, and get my wildlife conservation message out there to more people. And that is what means so much to me and my family.”

As for how his dad Steve would have reacted to the photos? Irwin laughs.

“There’d probably be a few ‘Crikeys’ thrown around!”

Bonds is available exclusively in the U.S. on Amazon and at bondsaustralia.com.