Get your fix of vitamin D at Praia da Arnela. Once you've worked on your tan, stick around and watch the sky dance with different colors as the sun slowly sets.
You're spoiled for sightseeing choice when visiting Spain. Praia da Arnela is a good place to begin here, but there are lots of other fine attractions to visit. Castro de Barona, Ría de Muros e Noia, and Praia da Rocha are not far from the stretch of coastline and will fill in your day nicely.