It's not Waterworld, but it's worth considering how many of the world's major cities are on the coast.
Also, and probably far more destructive than rising waters, is the inevitable climate change. The salt content in the oceans would shift, as well as temperature, changing ocean currents. Large areas of land would become water surface, changing wind patterns. Even the reduction in reflectivity due to lack of white ice and snow would impact weather patterns.
All of that means that such a world would be completely different in climate: a continuation of issues like the Sahara, which was once heavily forested with plenty of rain
. The world's farmland might not drown, but it might not be any good for growing crops. It's unknown what storms or hurricanes might occur. Without doubt, many plants and animals would be unable to adapt to new climates and mass extinctions would occur on staggering levels.