According to my knowledge: All the babies have the ability to hold their breath underwater when they are born & a few weeks after. That's why some parents take their babies with them when they go swimming. And you can see some 'swimming pool babies' like this!  ^_^ 

( If their parents don't do that - the babies lose this ability after some time & they have to learn how to swim again when they are a bit older. Or some people never learn how to swim )