Zac boosts his immune system in the Amazon rainforest before climbing a tree, exploring ayahuasca tourism and watching his dinner wriggle on a plate.

In between getting an up-close look at Iceland's renewable energy efforts, Zac soaks in a spa with Darin, samples reindeer and views natural wonders.

Following a crash course in apple growing, Zac and Darin head to Peru to delve into potato cryopreservation, biopiracy and the sport of sandboarding.

In the devastating wake of Hurricane Maria, Zac explores sustainability in the region, where he meets chef José Andrés, milks a goat and eats ceviche.

Before heading to Paris to learn about its tap water system, Zac joins pal Anna Kendrick for a lesson in H20, courtesy of a water sommelier in LA.

On an island that boasts a notable number of centenarians, Zac rethinks his view on nutrition as he ponders how the locals live such long, healthy lives.

After a beekeeping stop on a New York City rooftop, Zac checks out London's pollution-reduction efforts, from wall gardening to trash collecting.

Searching for ways to minimize their carbon footprint, Zac and Darin visit a self-sustaining home and other businesses innovating to reduce waste.

Zac and Darin try out life at a swanky eco-village committed to a small environmental footprint, visit a wildlife refuge and enjoy a zip lining trip.

Zac and Darin get down and dirty as they explore a natural approach to farming through regenerative agriculture and organic food production.

Leaders and representatives of Aboriginal communities show Zac and Darin how Indigenous cultures live to protect and preserve the land.

Eco-innovators introduce Zac and Darin to unique and cost-effective ways to address complex problems and help heal the environment.

From Sydney to the Greater Blue Mountains, Zac and Darin meet with leading eco-warriors to learn about protected lands and habitat conservation.

Zac and Darin test their cooking skills in Melbourne before heading to the Torres Strait Islands to understand the impact of rising sea levels.

In the aftermath of a devastating bushfire season, Zac and Darin learn about efforts to rehabilitate the wildlife and livestock population.

Along the coastline, Zac and Darin take a deep dive into the coral reef restoration techniques supporting a vast underwater ecosystem.