The inside of a termite mound proved especially challenging for Attenborough: it was so cramped that he could only face in one direction. He therefore had to slowly crawl backwards out of shot when performing re-takes.
The big blue is the world's greatest wilderness, far from shore and many kilometres deep. It's a vast marine desert where there is little to eat and nowhere to hide. Yet it's home to some of the biggest and most spectacular creatures on earth. This episode reveals what it takes to survive in this savage and forbidding world. We witness feats of incredible endurance, moments of high drama and extraordinary acts of heart-wrenching self-sacrifice. Every animal in the big blue must find their own unique way to survive.
As the expedition team near the end of their journey across Micronesia, it's a race against time for the extreme deep divers as they continue their search for new species. As Kate Humble explores the Rock Islands of Palau, Mike DeGruy embarks on a unique training programme. The Newtsuit is an incredible feat of submarine engineering - a bright yellow one-man submersible that Mike has to master before he can venture even deeper into the Pacific abyss.
Forty miles north of Honduras, near the Bay Island of Roatan, is a spectacular and pristinely preserved coral atoll: the Mesoamerican Reef. Explore the abundant and diverse marine life, lush vegetation, and magnificent caves of this rare underwater wonder.