The American marine biologist, explorer, author, and lecturer is one of the planets biggest advocates for the preservation of our oceans. Dr. Sylvia Earle should know the importance of this, as she’s still regularly exploring the depths at age 84.

She has been a National Geographic explorer-in-residence since 1998 and was the first female chief scientist of the U.S. National Oceanic and Atmospheric Administration. She was named by Time Magazine as its first Hero for the Planet in 1998. In this interview with Real Leaders, she explains why the oceans are critical for all life on earth.