Cayeux-sur-Mer is a resort town in the Somme department in Hauts-de-France in northern France. The town is part of the Baie de Somme - …Cayeux-sur-Mer is a resort town in the Somme department in Hauts-de-France in northern France. The town is part of the Baie de Somme - Picardie maritime regional natural park project. Its inhabitants are called the Cayolais.