Born in Boston, Greg is an ocean scientist who did early pioneering research in Antarctica on marine mammals and later ice ecology where he mastered the art of diving into icebergs. He was awarded the National Science Foundation/U.S. Navy Antarctic Service medal for research in the Antarctic and his book “Ice Island” was awarded the 2003 National Outdoor Book Award for Nature and the Environment.

Since 2000, Greg has led the effort to create one of the world's largest marine protected area around the Phoenix Islands in Kiribati using, for the first time, market-based mechanisms to conserve ocean biodiversity, which encourage economic opportunity for local communities. For this accomplishment he was named one of National Geographic Society's Heroes of 2007 and is considered an authority on these innovative marine conservation models.

Greg has a passion for marine technology and for communicating his work to the broader public; he was senior editor of the Marine Technology Society Journal, is a world authority on New Zealand's Hector's dolphin - one of the world's most endangered, an undersea technology and exploration specialist using deep-sea submersibles, produced an award-winning series of marine conservation films, and has lectured throughout the world. Greg has also written prolifically for science and popular publications including Nature and National Geographic Magazine.

He is a National Fellow of the Explorers Club, a recipient of the Pew Fellowship for Marine Conservation, an honorary associate professor at the Leigh Marine Laboratory at the University of Auckland, New Zealand, and was named one of the five "Bostonians of the Year" in 2008 by the Boston Globe ​​​