Practice holding your breath on the shore first, that is, let yourself sink, and then hold your breath in the water, so that you can float.

Practice this several times to ensure that you won't be flooded, and then learn some simple swimming strokes, such as straightening your hands and kicking the water with your feet. If your head sinks, hold your breath to make sure you don't suffocate.

So when you are mature, learn some simple swimming, such as breaststroke and freestyle.