The Black Tide

A perfect storm. An undersea earthquake like the ones which caused the Storegga Slides and a storm with gale force winds off the  charts wrecked the North Sea. A  massive wall of water estimated at 18 meters over high tide marks flooded much of North West Europe. Oil drilling rigs were wreaked and the oil spilled was sucked up along in the swells and deposited across miles of beaches, with some locations as far as 12 miles inland. 
Thousands of people died, cities were abandoned, millions were displaced. The economies of Norway, The Netherlands, much of Denmark and areas of the United Kingdom were ruined. Clean up and rebuilding efforts were slow and often stopped as other crisis developed.
The entirety of the North Sea coast is now a toxic waste. With the hulks of oil rigs, wreaked ships, ripped up undersea cables and lines strewn around like children's toys. 
Relief efforts are constantly hampered by recurring earthquakes and storms. With the return of magic, some local wildlife became awakened and uses their new powers to further hamper clean up efforts. Often attacking crews and researchers. 
There is an ever present worry and concern that another Black Tide could occur. Some early warning measures have been taken to help protect the region, however, these are more often than not located exclusively within corporate extraterritoriality zones. A few brave persons working in underfunded government centers tirelessly track storms and make their best efforts to predict another earthquake. No one wants to be in a place that suffers as ancient Doggerland did.
Not unexpectedly the scum of the earth gathered within this region. Criminals, anarchists, revolutionaries and terrorists all call the flooded coastal cities home. It is surprising that none of them have raised a flag and declared themselves to be a pirate republic. Perhaps it is fear of a corporate and government response that keeps them in check over this.