Northern France’s Opal Coast may be known for its wide sandy beaches, dunes and uninterrupted views of the Channel, but I didn’t count on being surrounded by sharks during my brush with its waters. But that’s the surprising - and enthralling - treat awaiting visitors to Boulogne, a seaside town that’s just two hours away from Dover but which takes visitors straight to the heart of French culture and history. And with beautiful countryside, old buildings to explore, markets to wander through and