Ile de Jean Charles underwater

Michael took on his longest and most gruelling journey yet - a 80,470km route around the Pacific Rim taking in Russia, China, Vietnam, Australia, New Zealand, and North and South America. This huge undertaking stretches him and the crew to their limits, and it sees him adopt a more investigative role, as he seeks to get under the skin of the places he visits - from a booming South Korea, to Colombia with its drug wars and poverty.

The team head to Oklahoma on the trail of 26 wolves who were secretly transported to a zoo. As temperatures soar, the vets must act fast to get them all out safely.

Australia is an island continent boasting nearly 35,000km of coastline. Humans come to the seaside to relax, but for tens of thousands of species that live and breed on our coast, it's a battleground.