The Bay of Biscay (Spanish: Golfo de Vizcaya, more commonly named as Mar Cantábrico, in English Cantabrian Sea; French: Golfe de Gascogne; Basque: Bizkaiko golkoa; Breton: Pleg-mor Gwaskogn; Gascon: Golf de Gasconha) is a gulf of the northeast Atlantic Ocean located south of the Celtic Sea. It lies along the western coast of France from Brest south to the Spanish border, and the northern coast of Spain west to Cape Ortegal, and is named in English after the province of Biscay, in the Spanish Basque Country.
The average depth is 1,744 metres (5,722 ft) and maximum depth is 5,049 metres (16,565 ft).
Castro Urdiales is a seaport of northern Spain, in the autonomous community of Cantabria, situated on the bay of Biscay. Castro Urdiales is a modern town, although its castle and the Gothic-style parish church of Santa María de la Asunción, date from the Middle Ages. Its chief industries are tourism, fishing, and the preservation of fish, especially sardines and anchovies, in oil. The "Lolin" and "La Castreña" anchovy canning factories serve as a reminder of the town's closeness to this industry and its proximity to the sea.
Tourism has greatly increased in Castro Urdiales in the last thirty years; many people from Bilbao and other parts of the Basque Country and Cantabria as well as Northern Spain in general keep summer homes in the town. Although the number of people registered in the town is around 32,000, the summer population can double or even triple this figure.The town is popular because of its beaches and scenic harbor. The commercial fishing industry is declining and may soon be eradicated completely.