Seafood (mariscos): on the coast, fresh seafood is widely available and quite affordable. In the inner regions, frozen (and poor quality) seafood can be frequently encountered outside few highly reputed (and expensive) restaurants. In coastal areas seafood deserves some attention, especially on the north Atlantic coast.
Quality seafood in Spain comes from Spain's northwestern region of Galicia. So restaurants with the words Gallego (Galician) will generally specialize in seafood. If you are feeling adventurous, you might want to try the Galician regional specialty Pulpo a la Gallega, which is boiled octopus served with paprika, rock salt and olive oil. Another adventurous option is Sepia which is cuttlefish, a relative of squid, or the various forms of Calamares (squid) that you can find in most seafood restaurants. If that isn't your style you can always order Gambas Ajillo (garlic shrimp), Pescado Frito (fried fish), Buñuelos de Bacalao (breaded and deep fried cod) or the ever-present Paella dishes. source: wikitvoyage.org