The best way to breathe while swimming depends on the swimming technique, but most techniques require swimmers to breathe in quickly and exhale slowly. Since swimmers' heads stay above water at all times during the back stroke, it allows for easy breathing.
During freestyle swimming, swimmers turn their head to the left or the right every few strokes to breathe in. Both the breast stroke and butterfly naturally place the swimmers head above water during each stroke, which allows swimmers to breathe in. Because breathing requires using a number of muscles, professional swimmers moderate their breathing carefully to maximum how they use their energy.