Charente Maritime oysters are reckoned to be the best in France. A trip to the oyster producing towns makes a great day out - even if you don't like oysters! The oysters are are bred in the mouth of the Suedre estuary and then grown on in special ponds, originally used by the Romans to collect salt.
From Royan, the closest oyster farms are at Mornac sur Seudre. Mornac is a charming village, another of "France's Most Beautiful Villages", with craft shops and good restaurants.
For larger scale oyster activities, head to La Tremblade, to the north of Mornac. Here you can see the oyster boats bring in sacks of oysters and mussels on the rising tide, and later feast on them in one of the many informal shacks along the "rade" - the causeway leading through the marshes to the open river. If seafood is not to your taste, there is also a good creperie, le Ponton.