What If All the World's Ice Melted?

Ice caps on both poles of the planet are melting. And not just a few. All of them. If all this ice melted, it would be catastrophic. How much would the sea levels rise? How would this impact global temperatures? And what would this mean for life on Earth? Would the coastal lands be completely submerged in water? What will happen to places like Denmark, the Maldives and Singapore?