For instance, a restaurant in Mumbai will probably give better quality seafood than a restaurant in Delhi or elsewhere. Because the chef there has been preparing seafood for longer, has probably had it many times, in their daily life, learned it from the family members. Also, the people of coastal area, have a very keen eye for what type of fish or seafood item to select, how to cut, also, which part of the seafood to use and more.
One reason could also be the air and water there, that gives the seafood a different taste as compared to other places or specifically landlocked places. The air and water of each area in a country is different and affected by the weather conditions, soils and such. And this in turn also affects the taste of food, so the air and water could very well affect how seafood taste in coastal areas as compared to landlocked places.