[mirimir]

Actually, much of the Netherlands is already "literally underwater", and most of it would be flooded by storm surges. It's just that there's a highly layered defense of dikes, dams and pumping stations. Next time in Amsterdam, check out the display at city hall.

Since the disastrous 1953 flood, they've installed humongous valves at the mouths of all estuaries (Delta Works). If sea level increases more than a meter or so, they'll need to modify it.