How come babies can swim underwater until a certain age?

This is one of the primitive reflexes which all newborn infants have, but which are lost as they grow past six months old. Many of these reflexes are to protect the baby and carry a survival advantage, but some have no benefit. In the swimming reflex, placing a baby facedown in water will cause them to kick and paddle. The aim is to buy enough time until someone can come and help. It carries risks, however, since the baby may swallow large quantities of water or aspirate it into their lungs. Another example is the palmar grasp, where placing an object (such as a finger or toy) into a baby’s palm will cause a strong grip.

Answered by Aneel Bhangu, How It Works contributor.