Why 'Ocean' is David Attenborough's most personal documentary yet, according to its creators. The National Geographic film, described by the team as Attenborough’s most personal

To learn more about the making of the film, Popular Science sat down with Toby Nowlan, one of the film’s directors, and marine ecologist and National Geographic Explorer Enric Sala. Answers have been condensed for clarity. Laura Baisas: What was the most surprising thing you learned about our oceans throughout the course of working on the film?