Quite a bit of the Norte is inland, however there is a coastal walk which is distinct from the Camino de Santiago. I forget what it is called. I met a fellow at the albergue in San Esteban de Pravia (I think) who was walking this route. He showed me a leaflet with maps and details of accomodation which he had obtained from Tourist Info. I think he was intending to walk as far as La Coruna.
When I walked the Norte in May 2007, there were marked diversions to E-9, which is the coastal walking route. We took it whenever we saw it, because it meant beautiful coastal path walking. It always brought us back to the Camino. I noted some of those spots in my short summary of my walking stages, el-camino-del-norte/topic2829.html so I won't repeat them here. But I think it's usually a beautiful alternative to take the E-9, and I would go for it when you see the signs.
I would love to add a photo from the same stretch of the Norte: from Guemes to Santander. If you follow the route near the coast, instead of the red paved bicycle road, you will encounter breathtaking views as well as some very nice French peregrinas (I did! )