Thawing fish is necessary for both preparation and taste. Unlike some meats, such as beef, fish cannot be thawed at room temperature because seafood is much more susceptible to the growth of dangerous bacteria. The safest and easiest method for thawing a frozen fish is slowly over the course of the day. However, it must be kept cold during the thawing process.
Thaw the fish in the refrigerator. Place the fish in its original plastic or paper wrappings on a plate or inside of a bowl in the morning, and allow it to sit in the refrigerator until the evening. Thicker pieces of fish, such as steaks, take longer to thaw than thinner fillets. However, a full day in the fridge, usually six to eight hours, is enough to thaw most fish to a pliable state appropriate for cooking.
Place the fish under running water or in a bowl of cool water if you are pressed for time. If you do not have enough time to allow your fish to thaw in the fridge for the day, place the fish in a bowl in the sink. If the fish is wrapped in plastic, leave it inside the wrap. If the fish is wrapped in paper, remove it from the paper and place it in a plastic sipper bag. Run cool water over the fish and allow it to soak until it just begins to soften, usually between one to two hours. Avoid soaking naked fish in water as water may leach into the flesh and alter the taste.
Thaw the fish in your microwave only if it's absolutely necessary. Microwaving frozen fish can be risky because fish cooks relatively quickly, and some parts of the fish will thaw and cook more rapidly than other parts, turning your fish into a rubbery unpleasant mess.