Hot Springs in Southern Tuscany!! Here is a terrific blog post that will make you be sure to pack a swimsuit. The first bath she describes (Terme di Petriolo) is quite far from Benano, but Terme di Saturnia, Bagni San Filippo, Bagno Vignoni, and Terme di Chianciano are each about an hour's drive from Benano (give or take 10 minutes on either side of an hour). Acqua Borra is a little less than an hour and a half from Benano.
OK, none of these are exactly next door to Benano (the closest one on the list is almost an hour and a half away), but if you're willing to drive a bit, here are some recommendations for seaside lunches in Tuscany!