Which coast are you referring to?
The “Ruta del Mar de Arousa y Rio Ulla,” the “Route of the Sea of Arousa and the River Ulla,” was believed to be the route used to transport St. James' body to Iria Flavia. The boat carrying his body landed at Padron, on the Ulla River. In addition, this route was also followed by pilgrims who travelled by boat through the Mediterranean and up the coast, landing somewhere in the Bay of Arousa. I don't think this route qualifies one for a Compostela. For more info:
http://www.caminosantiago.org/cpperegri ... utamar.asp
Last year a group arranged a pilgrimage by sea - "El Camino de Santiago
sigue la ruta del mar " - starting at Valencia and calling in at these ports and towns: Valencia, Cartagena, Malaga, Cadiz, Lisbon, Vilagarcia de Arousa, Padrón and Santiago de Compostela.
The Deputy Director of Tourism of the regional government of Galicia, Xavier Valiño, said that this initiative aimed to "revitalize" the original route of pilgrimage. Perhaps the Asociación de Amigos del Camino de Santiago
de la región española de Valencia can give you more info?
Asociación Amigos del Camino de Santiago
de la Comunidad Valenciana.
C/ San Francisco de Borja, nº 10, 4º (46007)
963 859 982
Read more about the sea pilgrimage here: (Spanish)
http://www.ellitoral.com/index.php/diar ... IN-04.html