The Fethiye fish market is one of the best eating experiences on the Turkish coast. The concept is simple: you walk through the covered market, choose your fish from the stalls (sea bass, bream, red mullet, prawns, calamari — whatever is fresh), negotiate the price, and take it to one of the restaurants that ring the market. They cook it however you like — usually grilled — and serve it with salad, bread, and meze for a per-person charge on top of the fish price.
The market is in the old town, a short walk from the harbour. Go in the evening when the atmosphere is liveliest. The restaurants all offer roughly the same deal, so pick one that has a table you like and is not too aggressive with the touting. The quality of the fish is consistently excellent.