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The epic journey starts with a week of test dives in Chuuk Lagoon, the site of one of the most dramatic raids of World War II, before heading out to the remote Pacific islands. As their ship, the Big Blue Explorer, hits open ocean, the 2,000-mile journey of discovery is truly underway.

The second programme in the series sees the team of explorers travelling through some of the most remote islands of Micronesia. Kate Humble's scuba team encounter spectacular underwater wildlife while the extreme deep divers and scientists dive as deep as humans can without a submersible and continue to find fish that have never been seen before. In this environment, even the most experienced member of the deep team is not immune to unexpected equipment failure.

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.