A long-established freiduría a few minutes from the Sanctuary, Casa Paco is where locals come for fried fish done properly: light golden batter, hot oil, served on greaseproof paper with lemon and bread. The langostinos de Sanlúcar are the headline order — sweet, almost custardy, eaten with the fingers — but the boquerones, cazón en adobo (marinated dogfish), and tortillitas de camarones (shrimp fritters) are all reliable.
Cash works best for smaller orders. Get there early on summer evenings; queues can form.