In a video filmed at London’s Royal Festival Hall in  May and posted to Kensington Palace’s social media channels on Saturday, the biologist and natural historian reflected on the scale of human damage inflicted beneath the surface—much of it, he said, invisible to the public eye. “The awful thing is that it’s hidden from most people,” Attenborough said. “What we have done to the deep ocean floor is just unspeakably awful. If you did anything remotely like it on land, everybody would be up in arms.”

The pioneering naturalist added that he was “appalled” when he “first saw the footage taken for this film,” which revealed the state of the ocean floor. The feature-length documentary, Ocean with David Attenborough, explores “how his lifetime has coincided with the great age of ocean discovery” and “why a healthy ocean keeps the entire planet stable and flourishing.” The film will be available to stream online from Sunday, which is World Oceans Day.

“If this film does anything—if it just shifts public awareness—it will be very, very important,” Attenborough said. “I can only hope that people who see it will recognize that something must be done before we destroy this great treasure.” The 99-year-old broadcaster told William that it is “heartening” to have “an entrée into people’s front rooms.” “Whole families sitting at home in comfort can suddenly see this come to life. Films like this can reveal something entirely new,” he added.

Reflecting on the ocean’s unexplored frontiers, Prince William said the idea that there may be oceanic regions no human has ever seen was “fascinating.” He asked Attenborough whether that possibility still exists. “Beyond question,” the naturalist replied. “We’re in a situation now where it is possible to go into places where nothing like you has ever been before.”

The Prince of Wales added that the opportunity for discovery offers “a truly optimistic and exciting moment for the next generation—to become even greater explorers.” (CNN)