Floating motionless atop a tank of water in 2009, French diver Stéphane Mifsud claimed a world record for static apnea (stationary breath holding) of 11 minutes and 35 seconds. In 2010, another record setter, Ricardo da Gama Bahia of Brazil, flooded his body with oxygen for more than 20 minutes and then held his breath underwater for 20 minutes and 21 seconds. Both those achievements and many earlier records put to shame the breath-holding efforts of most people on dry land, who may nonetheless find that they, too, can hold out much longer than usual while swimming. The explanation, many say, is partly rooted in an evolved physiological response that helps seals, whales, otters and other aquatic mammals stay underwater for half an hour or more at a time: the diving reflex.