Davina travels to the Azores in the middle of the Atlantic Ocean, home to some of the world's deepest-diving creatures including whales. She investigates how animals cope with the pressures of diving - particularly the air-breathing animals - and begins by swimming with a school of dolphins. The ultimate diver in these waters is the sperm whale, capable of diving to over 2,000 metres and holding its breath for over 90 minutes. A world champion freediver teaches her how to swim alongside these huge creatures before she gets permission to take on the challenge.
