This reflex, also called the bradycardic response, causes babies to hold their breath and open their eyes when submerged, says Jeffrey Wagener, a pediatric pulmonologist in Denver. Parents can get this same reaction by blowing in their baby’s face. The response weakens as a baby gets older, but even adults have it to some degree.
Swedish researchers studying the dive reflex in 21 infants between 4 to 12 months old found that none of them inhaled water or choked during “diving” (being pulled underwater). They also noted that the babies didn’t seem apprehensive about the next dive. In fact, some seemed eager to dive again!
Many infant swim programs rely on the dive reflex to allow babies to “swim” before they’re old enough to hold their breath intentionally.