What freediving can reveal about human health — and our limits

What freediving can reveal about human health — and our limits Skip to content Subscribe today Every print subscription comes with full digital access Subscribe Now By Elizabeth Pennisi 3 hours ago Share this: Share Share via email (Opens in new window) Email Share on Facebook (Opens in new window) Facebook Share on Reddit (Opens in new window) Reddit Share on X (Opens in new window) X Print (Opens in new window) Print At 19, Tucker Francis was living his dream. About a decade earlier, he had sailed around the northwest Atlantic with his family, and his passion for the ocean and adventure blossomed. He loved snorkeling and recreational freediving, the loose term for diving deep underwater with no breathing gear. He would head down after the colorful creatures he spotted and stay underwater as long as possible to see as much as possible. Then, while chaperoning a 2017 snorkel trip in the U.S. Virgin Islands, Francis did one last freedive and disappeared. The boat’s captain found his body 10 meters down an hour later. Investigators later determined that Francis had suffered from a hypoxic blackout , also often called a shallow water blackout: He passed out when his brain couldn’t get enough oxygen — a problem that can come on without warning even among experienced swimmers. Once unconscious, the body sinks and the lungs can fill with water. Tucker Francis, 19, was on a recreational freedive when he experienced a shallow water blackout and died. Courtesy of the Francis Family The grieving Francis family decided to try to do something to reduce the risk of such blackouts among other freedivers. So they turned to integrative physiologist Erika Schagatay of Mid Sweden University in Östersund. She studies people who risk blacking out every day as they dive deeper than the Statue of Liberty is tall: competitive freedivers, also known as breath-hold divers or apneists. With help, the best of these divers can hold their breath for nearly 30 minutes — about as long as it