Take a deep dive. National Geographic's "Ocean with David Attenborough" brings "his greatest message" to life at 99-years-old and offers hope amid the ongoing climate crisis.

Big animals of the ocean go about their days mostly hidden from view. Scientists know these marine megafauna—such as whales, ...

PEOPLE has an exclusive first look at "Ocean with David Attenborough," a new National Geographic documentary featuring the 99-year-old naturalist exploring how to protect the world's oceans.