Eating well in Vinaròs means eating fish, and specifically the gamba roja (red prawn) for which the town is famous throughout Spain. The restaurants around the port on Passeig Colom and Passeig Marítim are where to go: a cluster of fish and seafood places that serve the morning's catch with minimal fuss. Prices are reasonable given the quality of the product.
Beyond the prawns, look for arròs a banda (rice cooked in fish stock, served separately from the fish), fideuà (the Valencian pasta version of paella cooked with noodles), and any whole grilled fish. The town is within the Valencian culinary tradition and the cooking at the better places is careful and locally focused.