The team travels to the Dominican Republic in the Caribbean to reveal the greatest secrets in the lives of the North Atlantic humpback whale; they witness a mother defend her calf in the ultimate ocean battle with a pack of orcas.

In the Azores, the team follows the elusive sperm whales to their hunting grounds a mile beneath the surface, where they discover the secret lives of these deep-diving whales.

The team is in the Azores to tag the sixgill shark and learn more about its nightly patterns hunting for food in the abyss; the team tags and retrieves valuable data, uncovering why this shark undertakes its epic journey from the depths at night.

The team's mission is to figure out if Svalbard's polar bears are adapting to their environment; they face this giant of the Arctic Ocean and scale a glacier to learn how much time is left for one of the most critical habitats for polar bears.

Learning how a population of bowhead whales, once hunted almost to extinction, is faring today; the team is the first to observe the feeding strategies of the deep-sea Greenland shark, an animal that can live for more than 400 years.