Not that easy to find but go in and join the locals that pack Zero Miglia. Fish and seafood could not be fresher since they are the fishermen of Nettuno. If the fish is not in season then they won't have it. If you're on a budget then go for whatever they have as "fish of the day" washed down with a carafe of local white:- excellent. If not budgeting then their wine list is pretty good.