Mission 31 was an undersea expedition organized by Fabien Cousteau. It was originally scheduled for November 2013, but was delayed to June 2014. On June 1, Cousteau and six crew members descended to the undersea laboratory Aquarius in the Florida Keys. Halfway through the expedition, three of crew were replaced, as had been planned. After 31 days, Cousteau and the crew ascended on July 2.
Throughout Mission 31, Cousteau's team conducted extended scuba diving expeditions to collect scientific data and IMAX footage. They hosted various one-day guests, conversed live with classrooms, and kept in touch with the outside world via social media. Cousteau estimated that his team collected the equivalent of two years' worth of surface dive data, enough for 10 scientific papers. Mission 31 was envisioned as a tribute to Cousteau's grandfather, Jacques Cousteau, who spent 30 days living underwater in 1963. Fabien Cousteau thus beat his grandfather's record for time spent underwater by a film crew by one day.