His first known scuba dive was an hour and a half buddy-breathing with a family friend in a swimming pool on his fourth birthday. Fabien Cousteau has made intensive study of sharks in their natural habitat, with the use of "Troy", a specially built "Trojan Shark" submarine designed and built by Eddie Paul of EPIndustries.com or Deadllinetv.net in the shape of a great white shark. He spent several hundred hours filming sharks in preparation for his documentary film on the subject, titled Mind of a Demon (CBS, June 28, 2006). He developed the idea of a shark-shaped submersible based on a childhood memory of the cover of a French-language comic book, The Adventures of Tintin: Le trésor de Rackham le rouge, which featured such a craft (which was purely imaginary at the time).
Fabien is the executive director and founder of Plant A Fish, a nonprofit dedicated to the restoration of the world's water bodies through active community engagement and education. It was founded on what would have been his grandfather's 100th birthday in 2010. He is actively involved in various environmental and ocean advocacy projects in the U.S. and overseas.