If the Antarctic Ice cap melts, sea level would rise a lot (more than 50 m), this would flood most cities in the world, so we would need to learn to breathe underwater!
Fortunately this is unlikely to happen, at least within a thousand years or so. What is more likely is that the ice that has melted from Greenland and from Antarctica will raise sea level by a metre or two. We will either have to adapt to this (for example by damming rivers and bilding levies around coastal cities) which would be very difficult and expensive, or we could try and prevent this from happening by reducing the amount of greenhouse gases we are emmitting.
As an aside, if the Arctic ice cap melts, it won’t raise the sea level at all. Do you know why?