And it should be noted that sea levels have been rising for longer than human civilization has existed. Loss of real estate and improvements because of natural shifts in land vs water levels is nothing new.

I would like to add that at any particular piece of the coast it is NOT the global ocean level rise that determines its fate. The edges of continents generally sink or rise, depending on what a particular tectonic plate is doing and what is the area's recent geological history (e.g. the Hudson Bay area is still rising having been freed from the weight of the glaciers after the last Ice Age ended, but the areas of coastal Maryland or Louisiana are geologically subsiding). There are also things like the silting up of river estuaries, rearrangement of barrier islands by hurricanes, etc. etc.