At the elite Navy Diving and Salvage Training Center in Panama City, Fla., they know how to figure out quickly who will be capable of accomplishing extremely dangerous underwater missions. They take young sailors and tie their hands behind their backs and bind their feet. They put the strap of a dive mask between the sailors' teeth and then throw them in the Olympic-size pool. The challenge is to stay afloat and live. "The more someone struggles," Morgan tells me, "the harder it is to get air and the more tired they get. You just have to inhibit the powerful, incredible instinct to breathe and your anxiety and alarm."