THE GREAT-GRANDSON OF OIL TYCOON JOHN D. ROCKEFELLER has been passionate about the ocean since he learned to sail at age 10. For more than 40 years now, David Rockefeller Jr. has raced and cruised the globe. In 2006, he started Sailors for the Sea, a nonprofit that educates sailors about conservation. He's also served as a member of the Pew Oceans Commission (pewtrusts.org), which has produced reports about the health of U.S. marine waters.

Q: Do you see irony in having become an environmentalist, given that your great-grandfather founded Standard Oil?

A: Not really. Today is so different from the late 1800s, when Standard Oil was started. We've added 5 billion people to the planet in the past century, and that has been the biggest factor in environmental degradation. And ironically, the discovery of oil in the ground probably saved a lot of whales.

"We can stop throwing plastic in the water. We can eat only sustainably caught fish." 
—David Rockefeller Jr.

Q: What do you think John D. would say about your environmental efforts?

A: Given that he started the Rockefeller Foundation and the Rockefeller Institute for Medical Research—now Rockefeller University—I think my great-grandfather would have looked at the environment as a challenge to science and to strategic philanthropy.

Q: When did you first become concerned about the environment?

A: Probably in the '60s. My mother gave us Rachel Carson's books when we were young. And fish began to disappear from our harbors in Maine.

Q: The book One Island, One Ocean (Weldon Owen, 2011) documents a 28,000-mile conservation journey sponsored by Sailors for the Sea. What does the title mean?

A: The idea is that the entire western hemisphere is a single island and the Atlantic and Pacific are a single ocean. If you drop a pail of water on your beach, you could pick up some of those same molecules on the other side of the world.