The Napa Valley is a surprisingly small wine region, just one eighth of the size of Bordeaux, but it is extremely well-endowed in the terroir department. Its varied soils and topography are vital to the valley’s greatness, whether it be the famous Rutherford dust, its red rock terraces or the deep, volcanic hillside soils of Stag’s Leap. Yet the most important influence on the place isn’t the land at all. It’s not even Stephen Spurrier, though his 1976 Paris tasting did put Napa on the map. It’s actually the sea.