Liz joins a team of scientists aboard a deep-sea submersible in search of an elusive ocean giant - the sunfish. She discovers how El Nino has effected the sea-lion population and helps with the tagging and tracking of hammerhead sharks.

Liz and the team see the impact humans have had on the oldest islands in the archipelago. Liz descends into a lava cave and meets a man working to protect giant tortoises. She dives to witness the birth of a new island.