Smith was a U.S. Navy veteran who, after separating, found a way to carry on his love affair with the ocean at the National Oceanographic and Atmospheric Administration, better known as NOAA. At this job, he spent a substantial amount of his time underwater. However, on May 5, 2009, the pressure waves from a nearby underwater jackhammer flipped through the settings of the electronics package of his breathing equipment and turned off the computer that was monitoring and controlling his supply of oxygen, without his knowledge or permission. He was using a specialized type of equipment called a mixed-gas rebreather, which recycles a diver’s breathing gas, injecting new oxygen to replace what the diver has already used up.

Dewey Smith was an extraordinarily experienced, skilled, and well-trained diver. Still, on that warm summer day in the Florida Keys, he breathed in the last remaining molecules of oxygen available to him, lost consciousness, and died. Nobody had done anything wrong, including him. Not really. Diving with a rebreather is the second most lethal activity in the world per hour, after BASE jumping. Once you remove from the statistics the weekend warriors who have heart attacks, about half of the all-too-frequent deaths are caused by the same phenomenon that killed Dewey: hypoxia, otherwise known as lack of oxygen. The divers almost never know what hit them, and the ocean rarely offers second chances.